Elutheronema rhadinum is a potentially commercial fisheries species and subjecting to intense exploitation in China.Knowledge on the population structure of E.rhadinum around the Chinese coastal waters was lacked, which was important for the rational exploitation and proper resource management of fish species.In the present study, genetic diversity and population structure of E.rhadinum were evaluated using a 564-base pair fragment of the mitochondrial cytochrome c oxidase subunit Ⅰ (CO Ⅰ) gene.A total of 76 specimens were collected from three localities around the East China Sea (Qidong and Zhoushan) and South China Sea (Zhuhai).Among these individuals, 9 polymorphic sites were detected and 11 distinct haplotypes were defined.High levels of haplotype diversity (h =0.759±0.035) and low levels of nucleotide diversity (nπ=0.00198±0.00326) were observed in E.rhadinum populations.The hierarchical analysis of molecular variance (AMOVA) indicated that 96.72% of the genetic variation occurred within the populations, whereas 3.28% of the genetic variation occurred among populations.No significant genealogical branches or clusters were recognized on the NJ tree.Intra-group variation among populations was significant ((g)st =0.03285, P<0.01).These results suggested that the E.rhadinum populations along the East China Sea and South China Sea have developed divergent genetic structures.Tests of neutral evolution and mismatch distribution suggested that E.rhadinum may have experienced a population expansion.The present study provides basic information for the conservation and sustainable exploitation of this species.