diff --git a/karbor/services/operationengine/engine/triggers/timetrigger/time_trigger.py b/karbor/services/operationengine/engine/triggers/timetrigger/time_trigger.py
index 777ec3d5..5235cd86 100644
--- a/karbor/services/operationengine/engine/triggers/timetrigger/time_trigger.py
+++ b/karbor/services/operationengine/engine/triggers/timetrigger/time_trigger.py
@@ -21,7 +21,7 @@ import six
 from stevedore import driver as import_driver
 
 from karbor import exception
-from karbor.i18n import _, _LE
+from karbor.i18n import _, _LE, _LW
 from karbor.services.operationengine.engine import triggers
 
 time_trigger_opts = [
@@ -212,31 +212,44 @@ class TimeTrigger(triggers.BaseTrigger):
                 int(timeutils.delta_seconds(entry_time, expect_run_time)) > 0):
             return expect_run_time
 
+        # The self._executor.execute_operation may have I/O operation.
+        # If it is, this green thread will be switched out during looping
+        # operation_ids. In order to avoid changing self._operation_ids
+        # during the green thread is switched out, copy self._operation_ids
+        # as the iterative object.
+        operation_ids = self._operation_ids.copy()
+        sent_ops = set()
         window = trigger_property.get("window")
         end_time = expect_run_time + timedelta(seconds=window)
-        if end_time <= entry_time:
-            LOG.error(_LE("Can not trigger operations to run. "
-                          "Because it is out of end time of window. "
-                          "expect run time=%(expect)s, end time=%(end)s, "
-                          "entry time=%(now)s"),
-                      {'expect': expect_run_time, 'end': end_time,
-                       'now': entry_time})
-        else:
-            # The self._executor.execute_operation may have I/O operation.
-            # If it is, this green thread will be switched out during looping
-            # operation_ids. In order to avoid changing self._operation_ids
-            # during the green thread is switched out, copy self._operation_ids
-            # as the iterative object.
-            operation_ids = self._operation_ids.copy()
-            for operation_id in operation_ids:
-                try:
-                    self._executor.execute_operation(
-                        operation_id, entry_time, expect_run_time, window)
-                except Exception:
-                    LOG.exception(_LE("Submit operation to executor "
-                                      "failed, id=%s"),
-                                  operation_id)
-                    pass
+
+        for operation_id in operation_ids:
+            if operation_id not in self._operation_ids:
+                # Maybe, when traversing this operation_id, it has been
+                # removed by self.unregister_operation
+                LOG.warn(_LW("Execuete operation %s which is not exist, "
+                             "ignore it"), operation_id)
+                continue
+
+            now = datetime.utcnow()
+            if now >= end_time:
+                LOG.error(_LE("Can not trigger operations to run. "
+                              "Because it is out of window time. "
+                              "now=%(now)s, end time=%(end_time)s, "
+                              "expect run time=%(expect)s, "
+                              "wating operations=%(ops)s"),
+                          {'now': now, 'end_time': end_time,
+                           'expect': expect_run_time,
+                           'ops': operation_ids - sent_ops})
+                break
+
+            try:
+                self._executor.execute_operation(
+                    operation_id, now, expect_run_time, window)
+            except Exception:
+                LOG.exception(_LE("Submit operation to executor "
+                                  "failed, operation id=%s"), operation_id)
+
+            sent_ops.add(operation_id)
 
         next_time = self._compute_next_run_time(
             expect_run_time, trigger_property['end_time'], timer)
diff --git a/karbor/tests/unit/operationengine/engine/triggers/timetrigger/test_time_trigger.py b/karbor/tests/unit/operationengine/engine/triggers/timetrigger/test_time_trigger.py
index 235eb388..1c3db892 100644
--- a/karbor/tests/unit/operationengine/engine/triggers/timetrigger/test_time_trigger.py
+++ b/karbor/tests/unit/operationengine/engine/triggers/timetrigger/test_time_trigger.py
@@ -165,6 +165,24 @@ class TimeTriggerTestCase(base.TestCase):
         trigger.unregister_operation(operation_id)
         self.assertNotIn(operation_id, trigger._operation_ids)
 
+    def test_unregister_operation_when_scheduling(self):
+        trigger = self._generate_trigger()
+
+        for op_id in ['1', '2', '3']:
+            trigger.register_operation(op_id)
+            self.assertTrue(op_id in trigger._operation_ids)
+        eventlet.sleep(0.5)
+
+        for op_id in ['2', '3']:
+            trigger.unregister_operation(op_id)
+            self.assertTrue(op_id not in trigger._operation_ids)
+        eventlet.sleep(0.6)
+
+        self.assertTrue(trigger._executor._ops['1'] >= 1)
+
+        self.assertTrue(('2' not in trigger._executor._ops) or (
+            '3' not in trigger._executor._ops))
+
     def test_update_trigger_property(self):
         trigger = self._generate_trigger()