Abstract: Objective To investigate the effect of high power microwave(HPM) on myocardial morphology and myocardial enzymes in rabbits.Methods Twenty-four adult rabbits(half male and half female) were randomly divided into four groups:a control group,high- (200 mW/cm²),moderate- (150 mW/cm²),and low-intensity(100 mW/cm²) radiation groups with the HPM exposure of 20 minutes.All experimental rabbits were sacrificed 6 hours after the treatment and their femoral artery blood samples were collected; the activities of myocardial enzymes were examined.The heart apex fresh tissues were taken immediately under ice bath and the pathological changes of the tissues were observed with light microscopy.Results Compared to those of the control group,the activities of serum creatine phosphokinase isoenzyme(CK-MB)(619.5±268.3 U/L),creatine phosphokinase(CK)(841.7±131.4 U/L),and lactate dehyrogenase(LDH)(376.5±149.6 U/L) increased significantly in the rabbits exposed to low-intensity(100 mW/cm²) radiation(P <0.05 for all).The pathological changes of the myocardial tissues were observed,with loose and light staining of cytoplasm,fracture of muscle fiber,angiectasis hyperemia of myocardial interstitium,and inflammatory cell infiltration.The pathological changes were positively correlated with the intensity of HPM exposure.Conclusion High power microwave radiation had damage effect on myocardial morphology and enzymes in rabbits.