diff --git a/resources/profiles/BBL/process/fdm_process_bbl_common.json b/resources/profiles/BBL/process/fdm_process_bbl_common.json
index 8e6e05fc4..3090f15ed 100644
--- a/resources/profiles/BBL/process/fdm_process_bbl_common.json
+++ b/resources/profiles/BBL/process/fdm_process_bbl_common.json
@@ -74,6 +74,7 @@
     "support_type": "normal(auto)",
     "support_on_build_plate_only": "0",
     "support_top_z_distance": "0.2",
+    "support_bottom_z_distance": "0.2",
     "support_filament": "0",
     "support_line_width": "0.42",
     "support_interface_loop_pattern": "0",
diff --git a/src/libslic3r/Preset.cpp b/src/libslic3r/Preset.cpp
index c3ac6b366..47ce65a4c 100644
--- a/src/libslic3r/Preset.cpp
+++ b/src/libslic3r/Preset.cpp
@@ -714,7 +714,7 @@ static std::vector<std::string> s_Preset_print_options {
     "support_angle", "support_interface_top_layers", "support_interface_bottom_layers",
     "support_interface_pattern", "support_interface_spacing", "support_interface_loop_pattern",
     "support_top_z_distance", "support_on_build_plate_only","support_critical_regions_only", "bridge_no_support", "thick_bridges", "max_bridge_length", "print_sequence",
-    "filename_format", "wall_filament",
+    "filename_format", "wall_filament", "support_bottom_z_distance",
     "sparse_infill_filament", "solid_infill_filament", "support_filament", "support_interface_filament",
     "ooze_prevention", "standby_temperature_delta", "interface_shells", "line_width", "initial_layer_line_width",
     "inner_wall_line_width", "outer_wall_line_width", "sparse_infill_line_width", "internal_solid_infill_line_width",
diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index 47d10284f..3e1d2092d 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -2430,6 +2430,15 @@ void PrintConfigDef::init_fff_params()
     def->mode = comAdvanced;
     def->set_default_value(new ConfigOptionFloat(0.2));
 
+    // BBS:MusangKing
+    def = this->add("support_bottom_z_distance", coFloat);
+    def->label = L("Bottom Z distance");
+    def->category = L("Support");
+    def->tooltip = L("The z gap between the bottom support interface and object");
+    def->sidetext = L("mm");
+    def->mode = comAdvanced;
+    def->set_default_value(new ConfigOptionFloat(0.2));
+
     def = this->add("enforce_support_layers", coInt);
     //def->label = L("Enforce support for the first");
     def->category = L("Support");
@@ -3733,7 +3742,7 @@ void PrintConfigDef::handle_legacy(t_config_option_key &opt_key, std::string &va
         , "support_sharp_tails","remove_small_overhangs", "support_with_sheath",
         "tree_support_branch_diameter_angle", "tree_support_collision_resolution",
         "small_perimeter_speed", "max_volumetric_speed", "max_print_speed",
-        "support_bottom_z_distance", "support_closing_radius",
+        "support_closing_radius",
         "remove_freq_sweep", "remove_bed_leveling", "remove_extrusion_calibration",
         "support_transition_line_width", "support_transition_speed", "bed_temperature", "bed_temperature_initial_layer",
         "can_switch_nozzle_type", "can_add_auxiliary_fan", "extra_flush_volume", "spaghetti_detector", "adaptive_layer_height"
diff --git a/src/libslic3r/PrintConfig.hpp b/src/libslic3r/PrintConfig.hpp
index 22360c902..6dceaedfc 100644
--- a/src/libslic3r/PrintConfig.hpp
+++ b/src/libslic3r/PrintConfig.hpp
@@ -619,6 +619,7 @@ PRINT_CONFIG_CLASS_DEFINE(
     ((ConfigOptionBool,                support_on_build_plate_only))
     ((ConfigOptionBool,                support_critical_regions_only))
     ((ConfigOptionFloat,               support_top_z_distance))
+    ((ConfigOptionFloat,               support_bottom_z_distance))
     ((ConfigOptionInt,                 enforce_support_layers))
     ((ConfigOptionInt,                 support_filament))
     ((ConfigOptionFloat,               support_line_width))
diff --git a/src/libslic3r/PrintObject.cpp b/src/libslic3r/PrintObject.cpp
index 622f5a64e..68cb0f6be 100644
--- a/src/libslic3r/PrintObject.cpp
+++ b/src/libslic3r/PrintObject.cpp
@@ -707,6 +707,7 @@ bool PrintObject::invalidate_state_by_config_options(
 		} else if (
                opt_key == "elefant_foot_compensation"
             || opt_key == "support_top_z_distance"
+            || opt_key == "support_bottom_z_distance"
             || opt_key == "xy_hole_compensation"
             || opt_key == "xy_contour_compensation") {
             steps.emplace_back(posSlice);
diff --git a/src/libslic3r/Slicing.cpp b/src/libslic3r/Slicing.cpp
index 58bc4b150..36c04a523 100644
--- a/src/libslic3r/Slicing.cpp
+++ b/src/libslic3r/Slicing.cpp
@@ -113,8 +113,7 @@ SlicingParameters SlicingParameters::create_from_config(
     if (! soluble_interface) {
         params.gap_raft_object    = object_config.raft_contact_distance.value;
         //BBS
-        //params.gap_object_support = object_config.support_bottom_z_distance.value;
-        params.gap_object_support = object_config.support_top_z_distance.value;
+        params.gap_object_support = object_config.support_bottom_z_distance.value; 
         params.gap_support_object = object_config.support_top_z_distance.value;
         if (params.gap_object_support <= 0)
             params.gap_object_support = params.gap_support_object;
diff --git a/src/libslic3r/TreeSupport.cpp b/src/libslic3r/TreeSupport.cpp
index 50ea4b3aa..767239aed 100644
--- a/src/libslic3r/TreeSupport.cpp
+++ b/src/libslic3r/TreeSupport.cpp
@@ -2150,9 +2150,12 @@ void TreeSupport::draw_circles(const std::vector<std::vector<Node*>>& contact_no
                 {
                     if (layer_nr >= bottom_interface_layers + bottom_gap_layers)
                     {
-                        const Layer* below_layer = m_object->get_layer(layer_nr - bottom_interface_layers);
-                        ExPolygons bottom_interface = std::move(intersection_ex(base_areas, below_layer->lslices));
-                        floor_areas.insert(floor_areas.end(), bottom_interface.begin(), bottom_interface.end());
+                        for (size_t i = 0; i <= bottom_gap_layers; i++)
+                        {
+                            const Layer* below_layer = m_object->get_layer(layer_nr - bottom_interface_layers - i);
+                            ExPolygons bottom_interface = std::move(intersection_ex(base_areas, below_layer->lslices));
+                            floor_areas.insert(floor_areas.end(), bottom_interface.begin(), bottom_interface.end());
+                        }
                     }
                     if (floor_areas.empty() == false) {
                         floor_areas = std::move(diff_ex(floor_areas, avoid_region_interface));
diff --git a/src/slic3r/GUI/ConfigManipulation.cpp b/src/slic3r/GUI/ConfigManipulation.cpp
index f1774ec42..a5b3e49ed 100644
--- a/src/slic3r/GUI/ConfigManipulation.cpp
+++ b/src/slic3r/GUI/ConfigManipulation.cpp
@@ -530,7 +530,7 @@ void ConfigManipulation::toggle_print_fff_options(DynamicPrintConfig *config, co
     for (auto el : { "support_style", "support_base_pattern",
                     "support_base_pattern_spacing", "support_angle",
                     "support_interface_pattern", "support_interface_top_layers", "support_interface_bottom_layers",
-                    "bridge_no_support", "max_bridge_length", "support_top_z_distance",
+                    "bridge_no_support", "max_bridge_length", "support_top_z_distance", "support_bottom_z_distance",
                      //BBS: add more support params to dependent of enable_support
                     "support_type", "support_on_build_plate_only", "support_critical_regions_only",
                     "support_object_xy_distance", "independent_support_layer_height"})
diff --git a/src/slic3r/GUI/GUI_Factories.cpp b/src/slic3r/GUI/GUI_Factories.cpp
index 90b680f22..24213a04b 100644
--- a/src/slic3r/GUI/GUI_Factories.cpp
+++ b/src/slic3r/GUI/GUI_Factories.cpp
@@ -80,7 +80,7 @@ std::map<std::string, std::vector<SimpleSettingData>>  SettingsFactory::OBJECT_C
                     {"enable_support", "",4},{"support_type", "",5},{"support_threshold_angle", "",6},{"support_on_build_plate_only", "",7},
                     {"support_filament", "",8},{"support_interface_filament", "",9},
                      {"tree_support_branch_angle", "",10}, {"tree_support_wall_count", "",11},{"tree_support_with_infill", "",12},//tree support
-                            {"support_top_z_distance", "",13},{"support_base_pattern", "",14},{"support_base_pattern_spacing", "",15},
+                            {"support_top_z_distance", "",13},{"support_bottom_z_distance", "",24},{"support_base_pattern", "",14},{"support_base_pattern_spacing", "",15},
                             {"support_interface_top_layers", "",16},{"support_interface_bottom_layers", "",17},{"support_interface_spacing", "",18},{"support_bottom_interface_spacing", "",19},
                             {"support_object_xy_distance", "",20}, {"bridge_no_support", "",21},{"max_bridge_length", "",22},{"support_critical_regions_only", "",23}
                             }},
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index da9e43811..9aecf4ad8 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -2073,7 +2073,7 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame)
         "layer_height", "initial_layer_print_height", "min_layer_height", "max_layer_height",
         "brim_width", "wall_loops", "wall_filament", "sparse_infill_density", "sparse_infill_filament", "top_shell_layers",
         "enable_support", "support_filament", "support_interface_filament",
-        "support_top_z_distance", "raft_layers"
+        "support_top_z_distance", "support_bottom_z_distance", "raft_layers"
         }))
     , sidebar(new Sidebar(q))
     , notification_manager(std::make_unique<NotificationManager>(q))
diff --git a/src/slic3r/GUI/Tab.cpp b/src/slic3r/GUI/Tab.cpp
index 988847d18..7d4066650 100644
--- a/src/slic3r/GUI/Tab.cpp
+++ b/src/slic3r/GUI/Tab.cpp
@@ -1890,6 +1890,7 @@ void TabPrint::build()
         optgroup->append_single_option_line("tree_support_wall_count");
         optgroup->append_single_option_line("tree_support_with_infill");
         optgroup->append_single_option_line("support_top_z_distance", "support#top-z-distance");
+        optgroup->append_single_option_line("support_bottom_z_distance", "support#bottom-z-distance");
         optgroup->append_single_option_line("support_base_pattern", "support#base-pattern");
         optgroup->append_single_option_line("support_base_pattern_spacing", "support#base-pattern");
         //optgroup->append_single_option_line("support_angle");