The razor clam, Sinonovacula constricta, which belongs to Mollusca,Bivalvia,Veneroida,Solecurtidae,is a common shellfish as human seafood,living in the lower-to-mid intertidal zones along the coast of the West Pacific Ocean.The genetic structure of the razor clam has not been reported along the coast of Zhejiang and Fujian Provinces,the major aquaculture regions in China following the widespread culture.In this study,genetic structure of eight populations of S.constricta from Zhejiang and Fujian Provinces(NH,SM,YH,YQ,CL,HJ,HA and SS)was estimated by using microsatellite loci and mitochondria COⅠ sequences.Based on microsatellite loci,the effective allele gene(N_e)number ranged from 6.2 to 9.0,and the expected heterozygosity(H_e)was high,ranging from 0.806 to 0.875.Based on mitochondria COⅠ,haplotype diversity(Hd)ranged from 0.942 to 1.000 and nucleotide diversity(P)varied from 0.005 6 to 0.011 5. The analysis of genetic differentiation revealed that the F_ST values ranged from 0.001 4 to 0.063 8 based on microsatellite loci and from 0.000 9 to 0.368 0 based on mitochondria COⅠ.The phylogenetic tree analyses showed that the genetic relationships of eight populations were not consistent with a model of isolation by distance(IBD),but the populations within one bay could be clustered first.It is suggested that the razor clam contains high genetic diversity,but gene flow exists between Zhejiang populations and Fujian populations based on the genetic relationship.