56 taxa be longing to 23 famities, 2 classe (Gastropoda and Bivalvia) of Phylum Mollusca had been identified through the survey conducted at Degi lagoon (Binh Dinh province) in Oct 2009 and April 2010. Some of them have commercial value as Meretrix lyrata, Meretrix lusoria, Anomalocardia sp., Batillaria zonalis... Composition species at nearby estuary is higher than other station. The mean density of mollusca reached 13,543 inds./m2. Densities of Mollusca in dry season were higher than winter season. Density of mollusca at nearby estuary is higher than other areas.