This study investigated concentration of metal ions in sediment and intersexuality in Polymesoda erosa and Lutraria lutraria. Samples were collected from five areas of Ha Long Bay in October, 2012. The concentration of metal ions showed that Al (37390.0 ± 11816.5 mg/kg) was highest and Mn (360.4 ± 101.4 mg/kg) was second high concentration. Cd (0.04 ± 0.05 mg/kg) was lowest. The intersexuality was 14.3% in P. erosa and 9.1% in L. lutraria that observed only in female.