To explore the protein distribution and physicochemical properties differences between striated(ST)and smooth(SM) muscle of Patinopecten yessoensis, muscle tissue sections were stained with hematoxylin and eosin and observed under microscope. Protein composition was analyzed by SDS-PAGE. The physicochemical properties were compared by salt-soluble and Ca²⁺-ATPase.It was found that the striated muscle fibers were thicker and denser than smooth muscle . Myorod only existed in the smooth muscle and was not present in the striated muscle. The content of paramyosin in the smooth muscle was 31%, however, it was only 11% in striated muscle. There was a complete difference between the two kinds of salt solution curves. The smooth muscle solubility was characterized by S-shaped curve, which was different from the striated muscle and showed a linear rise in the range of 0.05–1.0 mol/L salt concentration. Such differences were probably caused by paramyosin content. In addition, the optimal temperature of Ca²⁺-ATPase in smooth muscle myofibrillar and striated muscle myofibrillar was 35 ℃ and 30 ℃, and the activation energy was 23.4 kJ/moL and 11.3 kJ/moL, respectively.