diff --git a/mace/python/tools/convert_util.py b/mace/python/tools/convert_util.py
index 2a685d322148a055fcec1a44d6dc52b09974a4ac..18791987f8f6ee9bdedca6a4107570d1a01a900a 100644
--- a/mace/python/tools/convert_util.py
+++ b/mace/python/tools/convert_util.py
@@ -13,26 +13,6 @@
 # limitations under the License.
 
 
-import tensorflow as tf
-from mace.proto import mace_pb2
-
-TF_DTYPE_2_MACE_DTYPE_MAP = {
-    tf.float32: mace_pb2.DT_FLOAT,
-    tf.half: mace_pb2.DT_HALF,
-    tf.int32: mace_pb2.DT_INT32,
-    tf.qint32: mace_pb2.DT_INT32,
-    tf.quint8: mace_pb2.DT_UINT8,
-    tf.uint8: mace_pb2.DT_UINT8,
-}
-
-
-def tf_dtype_2_mace_dtype(tf_dtype):
-    mace_dtype = TF_DTYPE_2_MACE_DTYPE_MAP.get(tf_dtype, None)
-    if not mace_dtype:
-        raise Exception("Not supported tensorflow dtype: " + tf_dtype)
-    return mace_dtype
-
-
 def mace_check(condition, msg):
     if not condition:
         raise Exception(msg)
diff --git a/mace/python/tools/converter.py b/mace/python/tools/converter.py
index fb5b8753ef0f4c604ea32e5f54b1a1c0da89eb7a..1da642629f97003456ba73a0a9a32ad7b7e8de6e 100644
--- a/mace/python/tools/converter.py
+++ b/mace/python/tools/converter.py
@@ -19,12 +19,9 @@ import os.path
 import copy
 
 from mace.proto import mace_pb2
-from mace.python.tools import tf_dsp_converter_lib
 from mace.python.tools import memory_optimizer
 from mace.python.tools import model_saver
 from mace.python.tools.converter_tool import base_converter as cvt
-from mace.python.tools.converter_tool import tensorflow_converter
-from mace.python.tools.converter_tool import caffe_converter
 from mace.python.tools.converter_tool import transformer
 from mace.python.tools.convert_util import mace_check
 
@@ -101,6 +98,7 @@ def main(unused_args):
 
     if FLAGS.runtime == 'dsp':
         if FLAGS.platform == 'tensorflow':
+            from mace.python.tools import tf_dsp_converter_lib
             output_graph_def = tf_dsp_converter_lib.convert_to_mace_pb(
                 FLAGS.model_file, FLAGS.input_node, FLAGS.output_node,
                 FLAGS.dsp_mode)
@@ -132,9 +130,11 @@ def main(unused_args):
             option.add_output_node(output_node)
 
         if FLAGS.platform == 'tensorflow':
+            from mace.python.tools.converter_tool import tensorflow_converter
             converter = tensorflow_converter.TensorflowConverter(
                 option, FLAGS.model_file)
         elif FLAGS.platform == 'caffe':
+            from mace.python.tools.converter_tool import caffe_converter
             converter = caffe_converter.CaffeConverter(option,
                                                        FLAGS.model_file,
                                                        FLAGS.weight_file)
diff --git a/mace/python/tools/tf_dsp_converter_lib.py b/mace/python/tools/tf_dsp_converter_lib.py
index 87bc92d0e3fea2384f2d733dde7bb3bc14e810dc..30236d5ce29c102eca3ce1140aa0221aca37f5cb 100644
--- a/mace/python/tools/tf_dsp_converter_lib.py
+++ b/mace/python/tools/tf_dsp_converter_lib.py
@@ -19,13 +19,29 @@ from tensorflow import gfile
 from operator import mul
 from dsp_ops import DspOps
 from mace.python.tools import graph_util
-from mace.python.tools.convert_util import tf_dtype_2_mace_dtype
 
 # converter --input ../libcv/quantized_model.pb \
 #           --output quantized_model_dsp.pb \
 #           --runtime dsp --input_node input_node \
 #           --output_node output_node
 
+TF_DTYPE_2_MACE_DTYPE_MAP = {
+    tf.float32: mace_pb2.DT_FLOAT,
+    tf.half: mace_pb2.DT_HALF,
+    tf.int32: mace_pb2.DT_INT32,
+    tf.qint32: mace_pb2.DT_INT32,
+    tf.quint8: mace_pb2.DT_UINT8,
+    tf.uint8: mace_pb2.DT_UINT8,
+}
+
+
+def tf_dtype_2_mace_dtype(tf_dtype):
+    mace_dtype = TF_DTYPE_2_MACE_DTYPE_MAP.get(tf_dtype, None)
+    if not mace_dtype:
+        raise Exception("Not supported tensorflow dtype: " + tf_dtype)
+    return mace_dtype
+
+
 padding_mode = {
     'NA': 0,
     'SAME': 1,