This paper is based on an observation on mollusc's life in mangrove forest of sepanjang Island, Sumenep Regency, east Java. a total of 25 species of molluscs that belong to 12 families was found in the Island. However only 19 species were used to found in Sepanjang's mangrove, others were immigrants from the sea. This paper also discusses the mollusc's density, reproduction conservation and potency.