Abstract: Some researches revealed that the tenderization of fish muscle during postmortem was caused by the endogenous proteinase especially serine proteinase.A collagenolytic serine proteinase was purified from blue scad skeletal muscle to homogeneity by ammonium sulfate fractionation and chromatographies including DEAE-Sephacel, Q-Sepharose and Capto Q.The molecular weight of the enzyme was 60ku as detected by SDS-PAGE.The optimal pH and temperature of the purified enzyme were 9.0 and 40℃, respectively.The enzyme activity was inhibited by serine proteinase inhibitors such as Pefabloc SC, Benzamidine, MBTI, PMSF and LBTI.However, other proteinase inhibitors had no effect on serine proteinase.Substrate specificity experiment demonstrated that the enzyme showed high specificity towards Boc-Leu-Lys-Arg-MCA.Furthermore, the enzyme effectively hydrolyzed gelatin, native type-I collagen and myofibrillar proteins such as myosin heavy chain (MHC) , these datum suggested that this enzyme might play an important role during postmortem tenderization of fish muscle.