Abstract: Morphological differences among two Eriocheir japonicus populations collected from Suifen River and Hepu River and two Eriocheir sinensis populations from Changjiang and Liaohe River were studied based on cluster analyzing and discriminal analyzing on 17 morphological characters , and the hybrids of Eriocheir sinensis (♂) × Eriocheir japonicus(♀) was also researched as an assistant subject. The result of cluster analyzing showed that the five populations can be divided into two groups:one group concluded Suifen,Hepu, Liaohe and the hybrids ,and the Changjiang population was single. The discriminal analyzing also separated samples from changjiang and the other four populations. The mean accurancy rate of discrimination of female crabs and male crab were 74.2% and 75.4％ . In the long period of process of evolution, the mitten crabs in China mainland gradually came into being different local populations which greatly rely on the geological environment around.These local populations possessed strongly regionality on the growth. Eriocheir japonicus and Eriocheir sinensis could hybridize and breed naturally, so reproductive isolation principles didn’t exist between them.