diff --git a/src/libslic3r/GCode.cpp b/src/libslic3r/GCode.cpp
index 1997bed92..dfdcd226d 100644
--- a/src/libslic3r/GCode.cpp
+++ b/src/libslic3r/GCode.cpp
@@ -1859,6 +1859,7 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
 
     std::vector<const PrintInstance*> 					print_object_instances_ordering;
     std::vector<const PrintInstance*>::const_iterator 	print_object_instance_sequential_active;
+    std::vector<int> extruder_count;
     if (print.config().print_sequence == PrintSequence::ByObject) {
         // Order object instances for sequential print.
         print_object_instances_ordering = sort_object_instances_by_model_order(print);
@@ -1867,6 +1868,14 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
         print_object_instance_sequential_active = print_object_instances_ordering.begin();
         for (; print_object_instance_sequential_active != print_object_instances_ordering.end(); ++ print_object_instance_sequential_active) {
             tool_ordering = ToolOrdering(*(*print_object_instance_sequential_active)->print_object, initial_extruder_id);
+            //get extruder count
+            std::vector<int> object_extruder_count = tool_ordering.cal_most_used_extruder(print.config());
+            if (extruder_count.empty())
+                extruder_count = object_extruder_count;
+            else
+                for (size_t extruder_id = 0; extruder_id < object_extruder_count.size(); extruder_id++)
+                    extruder_count[extruder_id] += object_extruder_count[extruder_id];
+
             tool_ordering.sort_and_build_data(*(*print_object_instance_sequential_active)->print_object,initial_extruder_id);
             if ((initial_extruder_id = tool_ordering.first_extruder()) != static_cast<unsigned int>(-1)) {
                 //BBS: try to find the non-support filament extruder if is multi color and initial_extruder is support filament
@@ -1914,6 +1923,7 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
         // Find tool ordering for all the objects at once, and the initial extruder ID.
         // If the tool ordering has been pre-calculated by Print class for wipe tower already, reuse it.
         tool_ordering = print.tool_ordering();
+        extruder_count = tool_ordering.cal_most_used_extruder(print.config());
         tool_ordering.assign_custom_gcodes(print);
         if (tool_ordering.all_extruders().empty())
             // No object to print was found, cancel the G-code export.
@@ -1989,6 +1999,15 @@ void GCode::_do_export(Print& print, GCodeOutputStream &file, ThumbnailsGenerato
         file.write(m_writer.set_additional_fan(0));
     }
 
+    //set key for most used extruder
+    //count most used extruder
+    int max_count_extruder = 0;
+    for (int extruder_id = 1; extruder_id < extruder_count.size(); extruder_id++) {
+        if (extruder_count[extruder_id] >= extruder_count[max_count_extruder])
+            max_count_extruder = extruder_id;
+    }
+
+    m_placeholder_parser.set("most_used_physical_extruder_id", print.config().physical_extruder_map.values[max_count_extruder]);
     // Let the start-up script prime the 1st printing tool.
     m_placeholder_parser.set("initial_tool", initial_extruder_id);
     m_placeholder_parser.set("initial_extruder", initial_extruder_id);
diff --git a/src/libslic3r/GCode/ToolOrdering.cpp b/src/libslic3r/GCode/ToolOrdering.cpp
index fe61df89f..b78dd3ed9 100644
--- a/src/libslic3r/GCode/ToolOrdering.cpp
+++ b/src/libslic3r/GCode/ToolOrdering.cpp
@@ -876,6 +876,27 @@ void ToolOrdering::collect_extruder_statistics(bool prime_multi_material)
     }
 }
 
+std::vector<int> ToolOrdering::cal_most_used_extruder(const PrintConfig &config)
+{
+    // record
+    std::vector<int> extruder_count;
+    extruder_count.resize(config.nozzle_diameter.size(), 0);
+    for (LayerTools &layer_tools : m_layer_tools) {
+        std::vector<unsigned int> filaments = layer_tools.extruders;
+        std::set<int> layer_extruder_count;
+        //count once only
+        for (unsigned int &filament : filaments) {
+            layer_extruder_count.insert(config.filament_map.values[filament] - 1);
+        }
+
+        //record
+        for (int extruder_id : layer_extruder_count) {
+            extruder_count[extruder_id]++;
+        }
+    }
+    return extruder_count;
+}
+
 std::set<std::pair<std::vector<unsigned int>, std::vector<unsigned int>>> generate_combinations(const std::vector<unsigned int> &extruders)
 {
     int                                                                       n = extruders.size();
diff --git a/src/libslic3r/GCode/ToolOrdering.hpp b/src/libslic3r/GCode/ToolOrdering.hpp
index 8a5baf1a8..3580c49fa 100644
--- a/src/libslic3r/GCode/ToolOrdering.hpp
+++ b/src/libslic3r/GCode/ToolOrdering.hpp
@@ -248,6 +248,7 @@ public:
 
     // should be called after doing reorder
     FilamentChangeStats get_filament_change_stats(FilamentChangeMode mode);
+    std::vector<int>    cal_most_used_extruder(const PrintConfig &config);
 
 private:
     void				initialize_layers(std::vector<coordf_t> &zs);