The effects of 17β-HSD11 gene on gonad development and sex hormone synthesis in H. cumingii were investigated by RACE (Rapid-amplificiantion of cDNA ends), real-time quantitative (qRT-PCR), in situ hybridization (ISH) and 17β-estradiol injection. The results showed that the full length of 17β-HSD11 cDNA was 1 134 bp, including 5' UTR 40 bp, open reading frame (ORF) 923 bp, 3' UTR 171 bp. It coded 307 amino acids. 17β-HSD11 was highly expressed in the hepatopancreas and the gonad, and the ovary was significantly higher than the testis. ISH results showed that there were hybridization signals on oocyte, follicular membrane and egg membrane. The expression of 17β-HSD11 gene was inhibited in both male and female gonads after injection of 17β-estradiol at different mass concentrations. The expression of 17β-HSD11 gene was decreased by 33.38% in ovary and 37.74% in testis after injection of 17β-estradiol at low mass concentrations. Moreover, after high mass concentration injection, the expression of 17β-HSD11 gene was decreased by 57.78% in ovary and 61.31% in testis. From the above results, it was speculated that 17β-HSD11 was related to gonadal development and estrogen synthesis in H. cumingii.