Objective To study the protective effect of Trimetazidine on myocardial injury in mice.Methods 6 to 7 week-old male BALB/c mice were randomly divided into 3 groups at twelve for each group:normal saline (NS) group,ISO group and TMZ group,N.S group for blank control group,ISO group for damage group,TMZ as treatment group.After 4 weeks,cardiac index (HW/BW) was calculated,serum lactate dehydrogenase (LDH) activity were measured by enzyme standard method.Malondialdehyde(MDA) was detected by thiobarbituric acid method(TBA).Superoxide dismutase (SOD) activity were determined by WST-1 method.The concentrations of serum Klotho were measured by ELSIA.The cardiac muscular tissue was imbedded with paraffin and colored with HE,Massion and caspase-3.Results The experiment model meets the requirements.In TMZ groups' HW/BW,LDH activity and MDA level were significantly lower than those of the ISO group(P ＜ 0.01).SOD energy,concentration of Klotho was significantly higher than those of the ISO group(P ＜ 0.01).HE color results showed that the myocardial cell diameter of ISO group was obviously larger than that of NS group,combined with disordered muscle fibers and hyperplastic myocardial interstitial fibroblasts.The cardiomyocytes diameter of TMZ groups was much smaller than that of the ISO group.Masson color results showed that the level of collagen fiber distribution in the myocardial interstitial and hemal wall of TMZ group was lower than that of ISO group.Caspase 3 color results showed that the number of tan dye distribution was significantly lower in TMZ group than that of the ISO group(Color positive results showed obvious practical color distribution).Conclusion Trimetazidine could prevent myocardial injury and its mechanism might be related to raised Klotho level.