The contents of heavy metal Cd, Cu, Pb, As, Hg and Zn in shellfish were analyzed, and the space distributions and seasonal variation features of these heavy metals in oyster were discussed, according to the survey results of oysters, clams and pinnidaes from the coast of South China Sea in 2009. The statistics results showed that the contents of Cd, Cu, Pb, Hg, As and Zn in shellfish had obvious differences among various sampling areas, species and cultivation seasons. The Cu and Zn contents in oyster samples were much higher than those in clam and pinnidae samples. The diet exposure quantity of heavy metal in shellfish samples were calculated applying the crude point assessment method. The assessment results showed that, for a healthy adult, the exposure quantity of heavy metal by intake of oysters and clams was lower than the recommended values of JECFA. While the Cd exposure level by pinnidaes intake was higher than the recommended values of JECFA.