diff --git a/src/slic3r/GUI/Gizmos/GLGizmoSimplify.cpp b/src/slic3r/GUI/Gizmos/GLGizmoSimplify.cpp
index c43f215d9..d61033ec4 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmoSimplify.cpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmoSimplify.cpp
@@ -294,6 +294,7 @@ void GLGizmoSimplify::live_preview() {
         // wait until cancel
         if (m_worker.joinable()) {
             m_state = State::canceling;
+            m_dealy_process_cv.notify_one();
             m_worker.join();
         }
     }
@@ -304,20 +305,38 @@ void GLGizmoSimplify::live_preview() {
 
 void GLGizmoSimplify::process()
 {
-    class SimplifyCanceledException : public std::exception {
-    public:
-       const char* what() const throw() { return L("Model simplification has been canceled"); }
-    };
+    if (m_volume == nullptr) return;
+    if (m_volume->mesh().its.indices.empty()) return;
+    size_t count_triangles = m_volume->mesh().its.indices.size();
+    if (m_configuration.use_count &&
+        m_configuration.wanted_count >= count_triangles)
+        return;
 
-    if (!m_original_its.has_value())
+    // when not store original volume store it for cancelation
+    if (!m_original_its.has_value()) {
         m_original_its = m_volume->mesh().its; // copy
 
-    auto plater = wxGetApp().plater();
-    plater->take_snapshot(_L("Simplify ") + m_volume->name);
-    plater->clear_before_change_mesh(m_obj_index);
+        // store previous state
+        auto plater = wxGetApp().plater();
+        plater->take_snapshot(_L("Simplify ") + m_volume->name);
+        plater->clear_before_change_mesh(m_obj_index);
+    }
+    
     m_progress = 0;
     if (m_worker.joinable()) m_worker.join();
-    m_worker = std::thread([this]() {
+
+    m_worker = std::thread([this]() {        
+        {// delay before process
+            std::unique_lock<std::mutex> lk(m_state_mutex);
+            auto is_modify = [this]() { return m_state == State::canceling; };
+            if (m_dealy_process_cv.wait_for(lk, m_gui_cfg->prcess_delay, is_modify)) {
+                // exist modification
+                m_state = State::settings;
+                request_rerender();
+                return;
+            }
+        }
+
         // store original triangles        
         uint32_t triangle_count = (m_configuration.use_count) ? m_configuration.wanted_count : 0;
         float    max_error      = (!m_configuration.use_count) ? m_configuration.max_error : std::numeric_limits<float>::max();
@@ -357,6 +376,7 @@ void GLGizmoSimplify::process()
 }
 
 void GLGizmoSimplify::set_its(indexed_triangle_set &its) {
+    if (m_volume == nullptr) return; // could appear after process
     m_volume->set_mesh(its);
     m_volume->calculate_convex_hull();
     m_volume->set_new_unique_id();
diff --git a/src/slic3r/GUI/Gizmos/GLGizmoSimplify.hpp b/src/slic3r/GUI/Gizmos/GLGizmoSimplify.hpp
index b609c5cdd..793512344 100644
--- a/src/slic3r/GUI/Gizmos/GLGizmoSimplify.hpp
+++ b/src/slic3r/GUI/Gizmos/GLGizmoSimplify.hpp
@@ -7,6 +7,9 @@
 #include "GLGizmoPainterBase.hpp" // for render wireframe
 #include "admesh/stl.h" // indexed_triangle_set
 #include <thread>
+#include <mutex>
+#include <condition_variable>
+#include <chrono>
 #include <optional>
 #include <atomic>
 
@@ -47,6 +50,7 @@ private:
     void set_its(indexed_triangle_set &its);
     void create_gui_cfg();
     void request_rerender();
+
     // move to global functions
     static ModelVolume *get_volume(const Selection &selection, Model &model);
     static const ModelVolume *get_volume(const GLVolume::CompositeID &cid, const Model &model);
@@ -62,10 +66,14 @@ private:
     size_t m_obj_index;
 
     std::optional<indexed_triangle_set> m_original_its;
-    bool m_show_wireframe;
+    bool m_show_wireframe; 
 
     volatile bool m_need_reload; // after simplify, glReload must be on main thread
+
     std::thread m_worker;
+    // wait before process
+    std::mutex m_state_mutex;
+    std::condition_variable m_dealy_process_cv;
 
     enum class State {
         settings,
@@ -87,8 +95,14 @@ private:
 
         void fix_count_by_ratio(size_t triangle_count)
         {
-            wanted_count = static_cast<uint32_t>(
-                std::round(triangle_count * (100.f-decimate_ratio) / 100.f));
+            if (decimate_ratio <= 0.f) { 
+                wanted_count = static_cast<uint32_t>(triangle_count);
+                return;
+            } else if (decimate_ratio >= 1.f) {
+                wanted_count = 0;
+                return;
+            }
+            wanted_count = static_cast<uint32_t>(std::round(triangle_count * (100.f-decimate_ratio) / 100.f));
         }
     } m_configuration;
 
@@ -106,6 +120,10 @@ private:
 
         // trunc model name when longer
         size_t max_char_in_name = 30;
+
+        // to prevent freezing when move in gui
+        // delay before process in [ms]
+        std::chrono::duration<long int, std::milli> prcess_delay = std::chrono::milliseconds(250);
     };
     std::optional<GuiCfg> m_gui_cfg;
 
@@ -122,6 +140,16 @@ private:
     void free_gpu();
     GLuint m_wireframe_VBO_id, m_wireframe_IBO_id;
     size_t m_wireframe_IBO_size;
+
+    // cancel exception
+    class SimplifyCanceledException: public std::exception
+    {
+    public:
+        const char *what() const throw()
+        {
+            return L("Model simplification has been canceled");
+        }
+    };
 };
 
 } // namespace GUI