diff --git a/imperative/python/megengine/__init__.py b/imperative/python/megengine/__init__.py
index 9a7cfc706d8b18768f086160ffdc93c3d5ef91ae..32aee56b0bde766d1f3504836ae35a6b22f8768e 100644
--- a/imperative/python/megengine/__init__.py
+++ b/imperative/python/megengine/__init__.py
@@ -78,7 +78,6 @@ from .logger import enable_debug_log, get_logger, set_log_file, set_log_level
 from .serialization import load, save
 from .tensor import Parameter, Tensor, tensor
 from .version import __version__
-from .utils import comp_graph_tools as cgtools
 
 _set_fork_exec_path_for_timed_func(
     sys.executable,
diff --git a/imperative/python/megengine/utils/comp_graph_tools.py b/imperative/python/megengine/utils/comp_graph_tools.py
index 2522e3f863045f0a4bdb58a5445895245bced93f..47cbb8fcff38395e8854c513ffb0e4232770c68b 100644
--- a/imperative/python/megengine/utils/comp_graph_tools.py
+++ b/imperative/python/megengine/utils/comp_graph_tools.py
@@ -15,6 +15,19 @@ from ..core._imperative_rt import OperatorNode, VarNode
 from ..core.tensor import megbrain_graph as G
 from ..core.tensor.raw_tensor import as_raw_tensor
 
+__all__ = [
+    "get_dep_vars",
+    "get_owner_opr_inputs",
+    "get_owner_opr_type",
+    "get_opr_type",
+    "graph_traversal",
+    "get_oprs_seq",
+    "replace_vars",
+    "replace_oprs",
+    "set_priority_to_id",
+    "load_and_inference",
+]
+
 
 def get_dep_vars(var: VarNode, var_type: str = None) -> List[VarNode]:
     """
@@ -166,7 +179,7 @@ def get_oprs_seq(outputs: List[VarNode], prune_reshape=False) -> List[OperatorNo
     # reshape op definition: reshape(input_tensor, dest_shape) -> output_tensor
     # when inferencing, shape of output_tensor is already known, so one can prune some operators related to dest_shape in the loaded graph
     def prune_reshape_oprs(outputs, oprs_seq, var2oprs):
-        def iterative_pruning(cur_opr, post_opr, marked_opr_ids):
+        def iterative_pruning(cur_opr, post_opr, marked_opr_ids, visited):
             useless = True
             for oup in cur_opr.outputs:
                 if "workspace" not in oup.name:
@@ -177,15 +190,20 @@ def get_oprs_seq(outputs: List[VarNode], prune_reshape=False) -> List[OperatorNo
             if useless:
                 marked_opr_ids.append(cur_opr.id)
 
-                for inp in cur_opr.inputs:
-                    iterative_pruning(inp.owner, cur_opr, marked_opr_ids)
+                for opr in set([var.owner for var in cur_opr.inputs]):
+                    if (opr.id, cur_opr.id) not in visited:
+                        visited.add((opr.id, cur_opr.id))
+                        iterative_pruning(opr, cur_opr, marked_opr_ids, visited)
 
         reshape_vars = get_dep_vars(outputs, "Reshape")
         reshape_oprs = [var.owner for var in reshape_vars]
 
         marked_opr_ids = []
+        visited = set()
         for reshape_opr in reshape_oprs:
-            iterative_pruning(reshape_opr.inputs[1].owner, reshape_opr, marked_opr_ids)
+            iterative_pruning(
+                reshape_opr.inputs[1].owner, reshape_opr, marked_opr_ids, visited
+            )
 
         # filter out all marked oprs
         return list(filter(lambda x: x.id not in marked_opr_ids, oprs_seq))
diff --git a/imperative/python/test/unit/test_cgtools.py b/imperative/python/test/unit/test_cgtools.py
index 3f0f341e1f7f06d52e27939d093bbb75b626cc36..c90760b488f6664282db9c323bcaf8bd44592ec1 100644
--- a/imperative/python/test/unit/test_cgtools.py
+++ b/imperative/python/test/unit/test_cgtools.py
@@ -13,9 +13,10 @@ import pytest
 import megengine
 import megengine.functional as F
 import megengine.module as M
-from megengine import cgtools
+import megengine.utils.comp_graph_tools as cgtools
 from megengine.core.tensor import megbrain_graph as mgb_graph
 from megengine.core.tensor.raw_tensor import as_raw_tensor
+from megengine.core.tensor.utils import astensor1d
 from megengine.jit import trace
 
 
@@ -98,3 +99,38 @@ def test_load_refcnt():
     graph, _, (varnode,) = mgb_graph.load_graph(io.BytesIO(buf))
     del graph
     varnode.owner
+
+
+def test_get_opr_seq():
+    class Net(M.Module):
+        def __init__(self):
+            super().__init__()
+            self.data = megengine.tensor(
+                np.random.random((1, 1, 4, 4)), dtype=np.float32
+            )
+
+        def forward(self, input):
+            A = input.shape[0]
+            shape = astensor1d((A, A), self.data, dtype="int32", device=input.device)
+            x = F.reshape(self.data, shape)
+            o = input + x
+            return o
+
+    net = Net()
+    input = megengine.tensor(np.random.random((4, 4)), dtype=np.float32)
+
+    @trace(symbolic=True, capture_as_const=True)
+    def func(inp, *, net=None):
+        return net(inp)
+
+    func(input, net=net)
+    file = io.BytesIO()
+    func.dump(file, optimize_for_inference=False)
+    file.seek(0)
+    *_, outputs = mgb_graph.load_graph(file)
+
+    seq_1 = cgtools.get_oprs_seq(outputs, True)
+    assert len(seq_1) == 5
+
+    seq_2 = cgtools.get_oprs_seq(outputs, False)
+    assert len(seq_2) == 6
diff --git a/imperative/python/test/unit/test_tracing.py b/imperative/python/test/unit/test_tracing.py
index 32ec58f52adb5eb72134ce0722ab3f2d83319b6c..e0ce660f50931dadf46968a4aac6beaf8a6c05e7 100644
--- a/imperative/python/test/unit/test_tracing.py
+++ b/imperative/python/test/unit/test_tracing.py
@@ -14,7 +14,8 @@ import pytest
 
 import megengine.core.tensor.megbrain_graph as G
 import megengine.functional as F
-from megengine import cgtools, tensor
+import megengine.utils.comp_graph_tools as cgtools
+from megengine import tensor
 from megengine.core._trace_option import set_symbolic_shape
 from megengine.core.ops import builtin as ops
 from megengine.core.ops.builtin import Elemwise