diff --git a/dpdata/plugins/ase.py b/dpdata/plugins/ase.py
index c6a595ab..6b80ebdf 100644
--- a/dpdata/plugins/ase.py
+++ b/dpdata/plugins/ase.py
@@ -1,3 +1,4 @@
+import os
 from __future__ import annotations
 
 from typing import TYPE_CHECKING, Generator
@@ -313,6 +314,9 @@ def to_system(self, data, file_name: str = "confs.traj", **kwargs) -> None:
         file_name : str
             path to file
         """
+        if os.path.isfile(file_name):
+            os.remove(file_name)
+
         list_atoms = ASEStructureFormat().to_system(data, **kwargs)
         traj = Trajectory(file_name, "a")
         _ = [traj.write(atom) for atom in list_atoms]
@@ -329,6 +333,9 @@ def to_labeled_system(
         file_name : str
             path to file
         """
+        if os.path.isfile(file_name):
+            os.remove(file_name)
+
         list_atoms = ASEStructureFormat().to_labeled_system(data, *args, **kwargs)
         traj = Trajectory(file_name, "a")
         _ = [traj.write(atom) for atom in list_atoms]
diff --git a/tests/test_ase_traj.py b/tests/test_ase_traj.py
index efe3126d..98bc8bc0 100644
--- a/tests/test_ase_traj.py
+++ b/tests/test_ase_traj.py
@@ -70,10 +70,9 @@ def setUp(self):
 @unittest.skipIf(skip_ase, "skip ase related test. install ase to fix")
 class TestASEtraj4(unittest.TestCase, CompSys, IsPBC):
     def setUp(self):
-        system_1 = dpdata.System("ase_traj/MoS2", fmt="deepmd")
-        system_1.to(file_name="tmp.traj", fmt="ase/traj")
-        self.system_2 = dpdata.System("tmp.traj", fmt="ase/traj")
-        self.system_1 = system_1
+        self.system_1 = dpdata.System("ase_traj/MoS2", fmt="deepmd")
+        self.system_1.to(file_name="ase_traj/tmp.traj", fmt="ase/traj")
+        self.system_2 = dpdata.System("ase_traj/tmp.traj", fmt="ase/traj")
         self.places = 6
         self.e_places = 6
         self.f_places = 6
@@ -83,10 +82,9 @@ def setUp(self):
 @unittest.skipIf(skip_ase, "skip ase related test. install ase to fix")
 class TestASEtraj4Labeled(unittest.TestCase, CompLabeledSys, IsPBC):
     def setUp(self):
-        system_1 = dpdata.LabeledSystem("ase_traj/MoS2", fmt="deepmd")
-        system_1.to(file_name="tmp1.traj", fmt="ase/traj")
-        self.system_2 = dpdata.LabeledSystem("tmp1.traj", fmt="ase/traj")
-        self.system_1 = system_1
+        self.system_1 = dpdata.LabeledSystem("ase_traj/MoS2", fmt="deepmd")
+        self.system_1.to(file_name="ase_traj/tmp1.traj", fmt="ase/traj")
+        self.system_2 = dpdata.LabeledSystem("ase_traj/tmp1.traj", fmt="ase/traj")
         self.places = 6
         self.e_places = 6
         self.f_places = 6