diff --git a/deepmd/pt/utils/env_mat_stat.py b/deepmd/pt/utils/env_mat_stat.py
index fa97203c89..2f3c728c99 100644
--- a/deepmd/pt/utils/env_mat_stat.py
+++ b/deepmd/pt/utils/env_mat_stat.py
@@ -128,38 +128,27 @@ def iter(
                 # TODO: export rcut_smth from DescriptorBlock
                 self.descriptor.rcut_smth,
             )
+            # reshape to nframes * nloc at the atom level,
+            # so nframes/mixed_type do not matter
             env_mat = env_mat.view(
-                coord.shape[0], coord.shape[1], self.descriptor.get_nsel(), 4
+                coord.shape[0] * coord.shape[1], self.descriptor.get_nsel(), 4
             )
-
-            if "real_natoms_vec" not in system:
-                end_indexes = torch.cumsum(natoms[0, 2:], 0)
-                start_indexes = torch.cat(
-                    [
-                        torch.zeros(1, dtype=torch.int32, device=env.DEVICE),
-                        end_indexes[:-1],
-                    ]
-                )
-                for type_i in range(self.descriptor.get_ntypes()):
-                    dd = env_mat[
-                        :, start_indexes[type_i] : end_indexes[type_i], :, :
-                    ]  # all descriptors for this element
-                    env_mats = {}
-                    env_mats[f"r_{type_i}"] = dd[:, :, :, :1]
-                    env_mats[f"a_{type_i}"] = dd[:, :, :, 1:]
-                    yield self.compute_stat(env_mats)
-            else:
-                for frame_item in range(env_mat.shape[0]):
-                    dd_ff = env_mat[frame_item]
-                    atype_frame = atype[frame_item]
-                    for type_i in range(self.descriptor.get_ntypes()):
-                        type_idx = atype_frame == type_i
-                        dd = dd_ff[type_idx]
-                        dd = dd.reshape([-1, 4])  # typen_atoms * nnei, 4
-                        env_mats = {}
-                        env_mats[f"r_{type_i}"] = dd[:, :1]
-                        env_mats[f"a_{type_i}"] = dd[:, 1:]
-                        yield self.compute_stat(env_mats)
+            atype = atype.view(coord.shape[0] * coord.shape[1])
+            # (1, nloc) eq (ntypes, 1), so broadcast is possible
+            # shape: (ntypes, nloc)
+            type_idx = torch.eq(
+                atype.view(1, -1),
+                torch.arange(
+                    self.descriptor.get_ntypes(), device=env.DEVICE, dtype=torch.int32
+                ).view(-1, 1),
+            )
+            for type_i in range(self.descriptor.get_ntypes()):
+                dd = env_mat[type_idx[type_i]]
+                dd = dd.reshape([-1, 4])  # typen_atoms * nnei, 4
+                env_mats = {}
+                env_mats[f"r_{type_i}"] = dd[:, :1]
+                env_mats[f"a_{type_i}"] = dd[:, 1:]
+                yield self.compute_stat(env_mats)
 
     def get_hash(self) -> str:
         """Get the hash of the environment matrix.