Nile tilapia (Oreochromis niloticus) is one of the widely cultured fish species in the world,and has been known as a good raw material in seafood processing field.In this paper,the changes of biochemical properties of muscle protein from Nile tilapia fillets sterilized by ozone treatment during iced storage were investigated by changes evaluation of myofibrillar protein salt solubility,Ca²⁺-ATPase activity,surface hydrophobicity of actomyosin,total sulfhydryl content of actomyosin and carbonyl content.The results showed that different degrees of protein degeneration of ozone-water pretreatment group and control group Nile tilapia fillets all occurred during iced storage.The myofibrillar protein salt solubility,Ca²⁺-ATPase activity and total sulfhydryl content all decreased as the storage time was extended.Moreover,both surface hydrophobicity of actomyosin and carbonyl content increased during iced storage.After being stored for 20 days,the myofibrillar protein salt solubility,Ca²⁺-ATPase activity and total sulfhydryl content of ozone-water pretreatment group decreased by 76.57%,89.76% and 66.72% respectively,while those of control group declined by 69.05%,86.45% and 62.29%.On the other hand,surface hydrophobicity of actomyosin and carbonyl content of ozone-water pretreatment group increased by 111.75% and 76.46% respectively,while those of control group rose by 104.77% and 58.23%.At the same storage time,the myofibrillar protein salt solubility,Ca²⁺-ATPase activity and total sulfhydryl content of ozone-water pretreatment group were lower than those of control group,and both surface hydrophobicity of actomyosin and carbonyl content were higher than those of control group.The research results indicated that the protein denaturation was promoted by the oxidation of ozone-water and ROS generated from ozone-water during storage period.