Abstract: Utilizing the IMP system of temperature measure, common technique of tissue section, analytical method of nutritious constituents, and taking salt-solubility and Ca ²⁺-ATPase activity as the index of protein denaturation, a comparative study was conducted to determine the effect of freezing on tissue structure of Meretrix linnaeus and Paphia undulata. The result showed that there was a obvious change on tissue structure of shellfish by freezing with moisture losing and non-protein content largely increasing, but the effect of freezing on protein denaturation of shellfish was little. However, protein denaturation of shellfish was evidently after two months of frozen storage. Under the same freezing condition, M.linnaeus always got larger influence than that of P.undulata. As a result, protein denaturation is more easily to occur in M.linnaeus than in P.undulata by freezing.