Based on 32 morphological characters of each mitten crab( Eriocheir sinensis or E . j aponicus) from six rivers, Liaohe, Huanghe, Yangtze, Oujiang, Pearl and Nanliujiang, Cluster analysis and discriminant analysis were conducted. In the result of cluster analysis, crabs from northern rivers, Liaohe, Huanghe, Yangtze and Oujiang were pooled into one group as E. sinensis, while crabs f rom southern rivers, Pearl and Nanliujiang were pooled into another group as E. japonicus . In discriminant analysis, crabs of northern rivers could be divided from southern rivers automatically, and the accuracy rate of discriminat ion was 100%. Mean accuracy rate of discrimination on crabs f rom northern rivers, Liaohe, Huanghe, Yangtze and Oujiang, was 86% . Yangtze was the lowest, 73% , while Huanghe was the highest, 97% . Mean accuracy rate of discrimination on crabs from southern rivers, Pearl and Nanliujiang, was 95%, Nanliujiang was 96% , Pearl was 94% . ANOVA was conducted on parameters highly contributed to distinguish the populations of mitten crab, and coefficients of difference were calculated. According to Mayr ( 1953) 75% rule, in this paper the results indicated that difference between crabs from northern and southern rivers was greater than difference between subspecies, while dif ference between crabs of four northern rivers and between crabs of two southern rivers belong to of population level.