diff --git a/paddle/py_paddle/dataprovider_converter.py b/paddle/py_paddle/dataprovider_converter.py
index cfb82e92d51c22467360a67a04d4bed4f6608e2e..6234dc65dcda59e7623239436e45c5a3dd27ec17 100644
--- a/paddle/py_paddle/dataprovider_converter.py
+++ b/paddle/py_paddle/dataprovider_converter.py
@@ -60,7 +60,7 @@ class IScanner(object):
         """
         pass
 
-    def finish_pre_scan(self, argument, dat=None):
+    def finish_pre_scan(self, argument):
         """
         Finish first scan pass. Allocate the memory.
 
@@ -103,23 +103,29 @@ class DenseScanner(IScanner):
 
     def pre_scan(self, dat):
         self.__height__ += 1
+        if self.__shape__ is None:
+            self.__shape__ = numpy.array(dat).shape
+            if len(self.__shape__) > 3:
+                raise ValueError(
+                    "The dimension of input cannot be greater than 3.")
+        else:
+            if self.__shape__ != numpy.array(dat).shape:
+                raise ValueError(
+                    "The data shape must be same in one mini-batch.")
 
-    def finish_pre_scan(self, argument, dat=None):
-        self.__shape__ = numpy.array(dat).shape
-        if len(self.__shape__) > 3:
-            raise ValueError("The dimension of input is greater than 3.")
+    def finish_pre_scan(self, argument):
         dim = reduce(lambda x, y: x * y, self.__shape__)
-        if len(self.__shape__) == 1:
-            assert dim == self.input_type.dim
+        if len(self.__shape__) == 1 and dim != self.input_type.dim:
+            raise ValueError("The data size must be equal to it in data layer.")
         self.__mat__ = numpy.ndarray(
             shape=(self.__height__, dim), dtype=numpy.float32)
         self.__height__ = 0
 
     def scan(self, dat):
-        if isinstance(dat, numpy.ndarray):
-            assert self.__shape__ == dat.shape
-            dat = dat.flatten()
-        self.__mat__[self.__height__] = dat
+        # It's better to use NumPy array for speed.
+        d = numpy.array(dat)
+        d = d.flatten()
+        self.__mat__[self.__height__] = d
         self.__height__ += 1
 
     def finish_scan(self, argument):
@@ -136,6 +142,7 @@ class DenseScanner(IScanner):
             h, w = self.__shape__[-2:]
             argument.setSlotFrameHeight(self.pos, h)
             argument.setSlotFrameWidth(self.pos, w)
+        self.__shape__ = None
 
 
 class SparseBinaryScanner(IScanner):
@@ -186,7 +193,7 @@ class IndexScanner(IScanner):
     def pre_scan(self, dat):
         self.__idx__ += 1
 
-    def finish_pre_scan(self, argument, dat=None):
+    def finish_pre_scan(self, argument):
         self.__ids__ = [0] * self.__idx__
         self.__idx__ = 0
 
@@ -211,8 +218,8 @@ class SequenceScanner(IScanner):
         for each in dat:
             self.__inner_scanner__.pre_scan(each)
 
-    def finish_pre_scan(self, argument, dat=None):
-        self.__inner_scanner__.finish_pre_scan(argument, dat)
+    def finish_pre_scan(self, argument):
+        self.__inner_scanner__.finish_pre_scan(argument)
 
     def scan(self, dat):
         self.__seq__.append(self.__seq__[-1] + self.get_size(dat))
@@ -253,11 +260,8 @@ class DataProviderConverter(object):
             for each_step, scanner in itertools.izip(each_sample, scanners):
                 scanner.pre_scan(each_step)
 
-        # Some scanners, like dense scanner, pre-allocate memory for mini-batch
-        # in finish_pre_scan function. The dat[0] is used to calculate the size
-        # of input data.
-        for scanner, each_feature in itertools.izip(scanners, dat[0]):
-            scanner.finish_pre_scan(argument, each_feature)
+        for scanner in scanners:
+            scanner.finish_pre_scan(argument)
 
         for each_sample in dat:
             for each_step, scanner in itertools.izip(each_sample, scanners):