Abstract: Culter alburnus( CA) were used to examine the tenderizing effects of compound phosphate,calcium chloride and papain by shearing stress in order to maintain the tenderness of semi- finished products from fresh water fish. Response surface methodology( RSM) and scanning electron microscope( SEM) were applied to optimize the tenderizer conditions and observe the surface microstructure of CA samples.The results showed that shearing force of CA samples was decreased significantly and the concentration of phosphate,calcium chloride and papain were 0.8‰¹.6‰,1.0‰².0‰ and 1.0‰².0‰ respectively.According to the results of RSM,the order influenced was chloride calcium( Ca Cl2) > phosphate > papain,the optimum composition of phosphate 1.3‰,Ca Cl21.6‰ and papain 1.5‰ was determined.Shearing force of CA samples was decreased to 0.073 kg / mm with optimum composition.In the case of surface microstructure results,the connective tissues in tenderized 1.0 h meat were less than it in the controls.Moreover,enlarged myofiber with cracks were observed on tenderized CA meat.In conclusion,obvious improvements on the meat tenderness were presented by the tenderizers at optimum composition.