Genetic data have aided fishery conservation research and management by facilitating the detection of genetically distinct populations, the measurement of genetic connectivity, and the identification of the risks associated with demographic change and inbreeding. is an important economic marine fish species in China and inhabits in the Bohai Sea, Yellow Sea, East China Sea and South China Sea. has become an important fishing target in the East China Sea since 1974. Its annual catches were once second only to has declined sharply since 1990 due to overfishing and ocean environmental change. To provide better protection and effective recovery for this species, it is urgent to evaluate its population structure and genetic diversity. However, population surveys of in China's coastal waters were rare. No population structure research based on molecular makers was available. In this study, we amplified the partial mitochondrial Cyt gene sequences of 176 individuals from six populations (Dalian, Qinhuangdao, Penglai, Rizhao, Zhoushan, and Shantou). The results showed that 32 polymorphic nucleotide sites and 30 haplotypes were detected among all the Cyt sequences. The haplotype diversity ranged from 0.883 to 0.953, and the nucleotide diversity was 0.0032-0.0039. This genetic diversity pattern was probably caused by a recent demographic expansion in the Pleistocene, a rapid population growth after 1970, and the adaptable biological characteristics of . Although the haplotype diversity was high, the genetic diversity is still vulnerable to overfishing. AMOVA analysis showed that the genetic differentiation of mainly occurred within the population variation. The genetic differentiations among populations were weak and no groups were identified. The high gene exchange among populations is probably caused by the seasonal migration behaviors of the adults and the long-distance transportation of juveniles by the Kuroshio (Black) Current. Demographic history analysis showed that the six populations experienced rapid population growth 0.17-0.42 Mya. This time point was within the middle Pleistocene. During this period, sea levels changed dramatically due to unstable temperatures. We speculate that the sea level changes during the middle Pleistocene might have had significant influence on the population expansion of . To our knowledge, this is the first population genetics research on in China's coastal waters based on molecular markers. This study could deepen our understanding of how to optimize the utilization of the natural resources of .