diff --git a/dpdata/plugins/ase.py b/dpdata/plugins/ase.py
index 4d0e0aed..a072b843 100644
--- a/dpdata/plugins/ase.py
+++ b/dpdata/plugins/ase.py
@@ -1,4 +1,5 @@
 from dpdata.format import Format
+import dpdata.ase.db
 
 
 @Format.register("ase/structure")
@@ -50,3 +51,22 @@ def to_labeled_system(self, data, *args, **kwargs):
             structures.append(structure)
 
         return structures
+
+
+@Format.register("db")
+@Format.register("ase/db")
+class ASEStructureFormat(Format):
+    @Format.post("rot_lower_triangular")
+    def from_labeled_system(self, file_name, begin = 0, step = 1) :
+        data = {}
+        data['atom_names'], \
+            data['atom_numbs'], \
+            data['atom_types'], \
+            data['cells'], \
+            data['coords'], \
+            data['energies'], \
+            data['forces'], \
+            tmp_virial, \
+            = dpdata.ase.db.get_frames(file_name, begin = begin, step = step)
+        return data
+
diff --git a/dpdata/system.py b/dpdata/system.py
index d7e4c410..b0b9345b 100644
--- a/dpdata/system.py
+++ b/dpdata/system.py
@@ -932,22 +932,6 @@ def has_virial(self) :
         # return ('virials' in self.data) and (len(self.data['virials']) > 0)
         return ('virials' in self.data)
 
-    @register_from_funcs.register_funcs('db')
-    @register_from_funcs.register_funcs('ase/db')
-    def from_ase_db(self, file_name, begin = 0, step = 1) :
-        self.data['atom_names'], \
-            self.data['atom_numbs'], \
-            self.data['atom_types'], \
-            self.data['cells'], \
-            self.data['coords'], \
-            self.data['energies'], \
-            self.data['forces'], \
-            tmp_virial, \
-            = dpdata.ase.db.get_frames(file_name, begin = begin, step = step)
-
-        # rotate the system to lammps convention
-        self.rot_lower_triangular()
-
     def affine_map_fv(self, trans, f_idx) :
         assert(np.linalg.det(trans) != 0)
         self.data['forces'][f_idx] = np.matmul(self.data['forces'][f_idx], trans)