diff --git a/python/paddle/fluid/contrib/int8_inference/utility.py b/python/paddle/fluid/contrib/int8_inference/utility.py
index b35d9f2424ccf093f70e75b13e23f6c5ad59e859..605dfdf53d0cb44972defcc3f86aa95982b82e41 100644
--- a/python/paddle/fluid/contrib/int8_inference/utility.py
+++ b/python/paddle/fluid/contrib/int8_inference/utility.py
@@ -634,7 +634,8 @@ class Calibrator(object):
                         break
                 starting_iter = int(0.6 * ending_iter)
         bin_width = hist_edeges[1] - hist_edeges[0]
-        P_sum = len(activation_blob)
+
+        P_sum = len(np.array(activation_blob).ravel())
         min_kl_divergence = 0
         min_kl_index = 0
         kl_inited = False