In this paper, mitochondrial COⅡ gene sequences with 693 bp were analyzed from Chinese mitten crab (Eriocheir sinensis) of the Yangtze Rive in China, the Thames River in the United Kingdom and the San Francisco Bay in U.S.A. 20 variable sites were found in the Yangtze River p opulation, 8 and 7 variable sites were found in the Thames River and the San Fra ncisco Bay populations, respectively. The haplotype diversities for the Yangtze River, Thames River and San Francisco Bay populations were 0.8433, 0.8158 and 0. 7821 respectively, and the nucleotide diversities were 0.0048, 0.0031 and 0.0039 , respectively. AMOVA analysis showed that significant genetic divergence existe d in populations of the Yangtze River with Thames River and San Francisco Bay, b ut there was not significant divergence between the Thames River and San Francis co Bay populations. Phylogenetic tree based on NJ methods and the analysis of Mi nimum Spanning Network all indicated that there would have occurred gene flow be tween the Times river and the San Francisco Bay populations. The results showed that the San Francisco Bay population could have originated from both China and Europe.