diff --git a/src/libslic3r/Format/bbs_3mf.cpp b/src/libslic3r/Format/bbs_3mf.cpp
index 69dd1e26e..aa5fd042d 100644
--- a/src/libslic3r/Format/bbs_3mf.cpp
+++ b/src/libslic3r/Format/bbs_3mf.cpp
@@ -7715,10 +7715,12 @@ public:
 
     void set_interval(long n) {
         boost::lock_guard lock(m_mutex);
+        BOOST_LOG_TRIVIAL(info) << __FUNCTION__ << " entry, and last interval is: " << m_interval;
         m_next_backup -= boost::posix_time::seconds(m_interval);
         m_interval = n;
         m_next_backup += boost::posix_time::seconds(m_interval);
         m_cond.notify_all();
+        BOOST_LOG_TRIVIAL(info) << __FUNCTION__ << " exit, and new interval is: " << m_interval;
     }
 
     void put_other_changes()
@@ -7796,6 +7798,7 @@ private:
     };
 private:
     _BBS_Backup_Manager() {
+        BOOST_LOG_TRIVIAL(info) << __FUNCTION__ << " inital and interval = " << m_interval;
         m_next_backup = boost::get_system_time() + boost::posix_time::seconds(m_interval);
         boost::unique_lock lock(m_mutex);
         m_thread = std::move(boost::thread(boost::ref(*this)));
@@ -7824,7 +7827,7 @@ private:
     }
 
     void process_ui_task(Task& t, bool canceled = false) {
-        BOOST_LOG_TRIVIAL(info) << "process_ui_task" << t.to_string();
+        BOOST_LOG_TRIVIAL(info) << "process_ui_task" << t.to_string() << " and interval = " << m_interval;
         switch (t.type) {
             case Backup: {
                 if (canceled)
@@ -7868,7 +7871,7 @@ private:
     }
 
     void process_task(Task& t) {
-        BOOST_LOG_TRIVIAL(info) << "process_task" << t.to_string();
+        BOOST_LOG_TRIVIAL(info) << "process_task" << t.to_string() << " and interval = " << m_interval;
         switch (t.type) {
             case Backup:
                 // do it in response
diff --git a/src/slic3r/GUI/MainFrame.cpp b/src/slic3r/GUI/MainFrame.cpp
index c0b4a9ece..3d88b6f97 100644
--- a/src/slic3r/GUI/MainFrame.cpp
+++ b/src/slic3r/GUI/MainFrame.cpp
@@ -573,7 +573,7 @@ DPIFrame(NULL, wxID_ANY, "", wxDefaultPosition, wxDefaultSize, BORDERLESS_FRAME_
         // BBS: backup project
         if (wxGetApp().app_config->get("backup_switch") == "true") {
             std::string backup_interval;
-            if (!wxGetApp().app_config->get("", "backup_interval", backup_interval))
+            if (!wxGetApp().app_config->get("app", "backup_interval", backup_interval))
                 backup_interval = "10";
             Slic3r::set_backup_interval(boost::lexical_cast<long>(backup_interval));
         } else {
diff --git a/src/slic3r/GUI/Preferences.cpp b/src/slic3r/GUI/Preferences.cpp
index 19ff1ffb3..fc709a67d 100644
--- a/src/slic3r/GUI/Preferences.cpp
+++ b/src/slic3r/GUI/Preferences.cpp
@@ -476,6 +476,8 @@ wxBoxSizer *PreferencesDialog::create_item_backup_input(wxString title, wxWindow
     StateColor input_bg(std::pair<wxColour, int>(wxColour("#F0F0F1"), StateColor::Disabled), std::pair<wxColour, int>(*wxWHITE, StateColor::Enabled));
     input->SetBackgroundColor(input_bg);
     input->GetTextCtrl()->SetValue(app_config->get(param));
+    wxTextValidator validator(wxFILTER_DIGITS);
+    input->GetTextCtrl()->SetValidator(validator);
 
 
     auto second_title = new wxStaticText(parent, wxID_ANY, _L("Second"), wxDefaultPosition, DESIGN_TITLE_SIZE, 0);
@@ -496,23 +498,22 @@ wxBoxSizer *PreferencesDialog::create_item_backup_input(wxString title, wxWindow
         e.Skip();
     });
 
-    input->GetTextCtrl()->Bind(wxEVT_TEXT_ENTER, [this, param, input](wxCommandEvent &e) {
+    std::function<void()> backup_interval = [this, param, input]() {
         m_backup_interval_time = input->GetTextCtrl()->GetValue();
         app_config->set("backup_interval", std::string(m_backup_interval_time.mb_str()));
         app_config->save();
         long backup_interval = 0;
         m_backup_interval_time.ToLong(&backup_interval);
         Slic3r::set_backup_interval(backup_interval);
+    };
+
+    input->GetTextCtrl()->Bind(wxEVT_TEXT_ENTER, [backup_interval](wxCommandEvent &e) {
+        backup_interval();
         e.Skip();
     });
 
-     input->GetTextCtrl()->Bind(wxEVT_KILL_FOCUS, [this, param, input](wxFocusEvent &e) {
-        m_backup_interval_time = input->GetTextCtrl()->GetValue();
-        app_config->set("backup_interval", std::string(m_backup_interval_time.mb_str()));
-        app_config->save();
-        long backup_interval = 0;
-        m_backup_interval_time.ToLong(&backup_interval);
-        Slic3r::set_backup_interval(backup_interval);
+     input->GetTextCtrl()->Bind(wxEVT_KILL_FOCUS, [backup_interval](wxFocusEvent &e) {
+        backup_interval();
         e.Skip();
     });