Effect of Siqi decoction on myocardial ischemia is to prevent cardiac myocyte membrane from damage associated with oxygen free radicals related to NO. To research the regulatoin of the content of malondialdehyde by Siqi decoction, an index of lipid peroxidation, via increasing activity of superoxide dismutase in blood serum of rats with Myocardial Ischemia, the model of myocardium ischemia was made in Wistar rats with posterior pituitary injection through vein in tail. Siqi decoction, Diaoxinxuekang(DK) and Fufangdanshenpian(FD), the latter two drugs of which are effective TCM drugs of anti-myocardial ischemia at present, were administrated to the rats with myocar-dium ischemia for 5 days to compare the effect of them on myocardium ischemia as reference drugs via measuring the changes of the content of malondialdehyde and the activity of superoxide dismutase in the rat blood serum with myocardial ischemia. There were a remarkable increase in the activity of superoxide dismutase and a decrease in the content of malondialdehyde in the serum of the rats administered Siqi decoction compared with those of the rats in control group, p<0.05. The contents of MDA in the serum of the prevention group rats in the experiments are lower than those of the cure group rats. Anti-Myocardium Ischemia mechanism of Siqi decoction is the regulation of the content of malondialdehyde via increasing activity of superoxide dismutase in the serum of Rats with myocardial ischemia and stimulating the activity of NOS in serum so as to increase NO concentration. Effect of Siqi decoction on myocardial ischemia is to prevent the action of myocyte membrane from damage associated with oxygen free radicals related to NO. To research the regulatoin of the content of malondialdehyde by Siqi decoction, an index of lipid peroxidation, via increasing activity of superoxide dismutase in Blood serum of rats with Myocardial Ischemia, the model of myocardium ischemia was made in Wistar rats with posterior pituitary injection through vein in tail. Siqi decoction, Diaoxinxuekang(DK) and Fufangdanshenpian(FD), the latter two drugs of which are effective TCM drugs Of anti-myocardial ischemia at present, were administrated to the rats with myocar-dium ischemia for 5 days to compare the effect of them on myocardium ischemia as reference drugs via measuring the changes of the content of malondialdehyde and the activity of superoxide dismutase in the Rat blood serum with myocardial ischemia. There were a significant increase in the activity of superoxide dismutase and ad Ecrease in the content of malondialdehyde in the serum of the rats administered Siqi decoction compared with those of the rats in control group, p<0.05. The contents of MDA in the serum of the prevention group rats in the experiments are lower than those of the Anti-Myocardium Ischemia mechanism of Siqi decoction is the regulation of the content of malondialdehyde via increasing activity of superoxide dismutase in the serum of Rats with myocardial ischemia and stimulating the activity of NOS in serum so as to increase NO concentration.