A swimming crab is one of the most economically important edible marine crabs in the East Asia area,and it is widely distributed in the coastal waters of China,Japan and Korea.To assess the level of genetic diversity and genetic variation of swimming crab populations along China coasts,the species from the six geographical populations from China Sea(Dalian,Dongying,Lianyungang,Zhangzhou,Zhoushan and Zhanjiang)were studied based on mitochondrial D-loop whole gene sequences.There were 1 141 bp,185 variation sites and 129 parsimony informative sites in D-loop whole gene sequences.And there were 48 haplotypes among 60 swimming crab individuals.Nucleotide diversity index and Haplotype diverstity index together revealed a high genetic diversity and low selective effect for swimming crab populations in China Sea.The genetic differential index F_ST of total six populations was 0.189 72,which meant that the genetic differentiation among populations was moderate and significant(P<0.05)and the inferred differentiation time was about(196.8-260.5)×10³ years.Low gene flow indicated that there were genetic differentiations among the fifteen groups,except between LYG and DY,ZJ,ZZ,respectively,in addition between ZJ and ZZ(N_em>5).Especially,there were pronounced levels of genetic differentiation between ZS and the others and a moderate genetic differentiation between DL and LYG,DY,ZJ and ZZ,respectively.The genetic distance had no significant correlation with geographical distance,so there may be more intricate reasons in population occurrence and spread.