Abstract: This paper studies on juvenile crab. 30 metric parameters representing morphological characters were measured and then analyzed comprehensively by the cluster analysis and the stepwise discrimination. (1) The results of cluster analysis shows : The morphology of juvenile Chinese mitten crab from Yangtze river is much similar to that from Oujiang river , but quite different from that of Liaohe river’s. (2) The result of stepwise discrimination based on 14 morphological parameters shows there is a significant difference among the populations ofjuvenilecrabfromthreerivers (P<0.01),thecorrectratesofdiscriminationare: 81.4%～88.4% (P1) and 82. 5% ～ 91. 4 % ( P2) . The discriminating efficiency is Liaohe > Oujiang > Yangtze. The average fitted probability is 85. 5 %. (3) The discriminant analysis , based on further selected 9 morphological parameters , with better contributions to the identification , give less average fitted probability -80. 4 % , but decrease the work amount in measurement and calculation significantly (36 %) , which is highly recommended to application in juvenile crab study.