diff --git a/tools/tiny-test-fw/CIAssignUnitTest.py b/tools/tiny-test-fw/CIAssignUnitTest.py
index 65bc89dc5e..091230f172 100644
--- a/tools/tiny-test-fw/CIAssignUnitTest.py
+++ b/tools/tiny-test-fw/CIAssignUnitTest.py
@@ -24,8 +24,8 @@ except ImportError:
 
 
 class Group(CIAssignTest.Group):
-    SORT_KEYS = ["config", "test environment", "multi_device", "multi_stage", "tags", "chip_target"]
-    MAX_CASE = 30
+    SORT_KEYS = ["test environment", "tags", "chip_target"]
+    MAX_CASE = 50
     ATTR_CONVERT_TABLE = {
         "execution_time": "execution time"
     }
@@ -47,13 +47,13 @@ class Group(CIAssignTest.Group):
             attr = Group.ATTR_CONVERT_TABLE[attr]
         return case[attr]
 
-    def _create_extra_data(self, test_function):
+    def _create_extra_data(self, test_cases, test_function):
         """
         For unit test case, we need to copy some attributes of test cases into config file.
         So unit test function knows how to run the case.
         """
         case_data = []
-        for case in self.case_list:
+        for case in test_cases:
             one_case_data = {
                 "config": self._get_case_attr(case, "config"),
                 "name": self._get_case_attr(case, "summary"),
@@ -72,19 +72,26 @@ class Group(CIAssignTest.Group):
             case_data.append(one_case_data)
         return case_data
 
-    def _map_test_function(self):
+    def _divide_case_by_test_function(self):
         """
-        determine which test function to use according to current test case
+        divide cases of current test group by test function they need to use
 
-        :return: test function name to use
+        :return: dict of list of cases for each test functions
         """
-        if self.filters["multi_device"] == "Yes":
-            test_function = "run_multiple_devices_cases"
-        elif self.filters["multi_stage"] == "Yes":
-            test_function = "run_multiple_stage_cases"
-        else:
-            test_function = "run_unit_test_cases"
-        return test_function
+        case_by_test_function = {
+            "run_multiple_devices_cases": [],
+            "run_multiple_stage_cases": [],
+            "run_unit_test_cases": [],
+        }
+
+        for case in self.case_list:
+            if case["multi_device"] == "Yes":
+                case_by_test_function["run_multiple_devices_cases"].append(case)
+            elif case["multi_stage"] == "Yes":
+                case_by_test_function["run_multiple_stage_cases"].append(case)
+            else:
+                case_by_test_function["run_unit_test_cases"].append(case)
+        return case_by_test_function
 
     def output(self):
         """
@@ -92,7 +99,6 @@ class Group(CIAssignTest.Group):
 
         :return: {"Filter": case filter, "CaseConfig": list of case configs for cases in this group}
         """
-        test_function = self._map_test_function()
 
         target = self._get_case_attr(self.case_list[0], "chip_target")
         if target:
@@ -104,14 +110,17 @@ class Group(CIAssignTest.Group):
             }
         else:
             overwrite = dict()
+
+        case_by_test_function = self._divide_case_by_test_function()
+
         output_data = {
             # we don't need filter for test function, as UT uses a few test functions for all cases
             "CaseConfig": [
                 {
                     "name": test_function,
-                    "extra_data": self._create_extra_data(test_function),
+                    "extra_data": self._create_extra_data(test_cases, test_function),
                     "overwrite": overwrite,
-                }
+                } for test_function, test_cases in case_by_test_function.iteritems() if test_cases
             ],
         }
         return output_data
@@ -158,6 +167,10 @@ class UnitTestAssignTest(CIAssignTest.AssignTest):
                         # case don't have this key, regard as filter success
                         filtered_cases.append(case)
                 test_cases = filtered_cases
+        # sort cases with configs and test functions
+        # in later stage cases with similar attributes are more likely to be assigned to the same job
+        # it will reduce the count of flash DUT operations
+        test_cases.sort(key=lambda x: x["config"] + x["multi_stage"] + x["multi_device"])
         return test_cases