Abstract: To investigate the effect of endogenous protease on the texture of Yesso scallop muscle during cold storage, the texture and protein change related indexes of Yesso scallop muscle was measured during 4 ℃ cold storage 7 d with a purpose to identify the functions of proteinases. The results showed that the hardness, springiness, chewiness and gumminess generally decreased during the whole cold storage process. SDS-PAGE analysis revealed that muscular proteins began to degrade obviously on the third day. In terms of enzyme activity, serine proteinase (SP) activity began to decrease sharply after 2 days of cold storage. Serine proteinase was purified from the muscle of Yesso scallop by ammonium sulfate precipitation, ion exchange chromatography, gel filtration and hydrophobic chromatography. SDS-PAGE and gelatin zymogram showed that in native condition SP was in homodimer form with molecular weight of 52 kDa. The optimum pH of SP was 9.0 and the optimum temperature was 37 ℃. SP specifically hydrolyzes substrates containing arginine or lysine residues at P₁ position on the carboxyl side. Serine protease specific inhibitors including PMSF, Leupeptin, Pefabloc SC and Benzamidine could inhibit the activity of SP by 97%, 98%, 90% and 85%, respectively. Metal ions Fe²⁺, Zn²⁺ and Cu²⁺ could also significantly suppress the activity of SP. SP could effectively degrade scallop myofibrillar at 37 ℃, which delivered a reference for revealing the effect of SP on the quality of Yesso scallop muscle protein.