Aim To observe the change of plasma nitric oxide (NO) of acute cerebral infracted patients and the influence of simvastatin on the level of plasma NO. Methods Using HNO3 deoxidize enzyme method, we examined the levels of plasma NO in 54 patients with cerebral infarction (They were devided into two groups at random: 31 patients in simvastatin therapy group and 23 patients in ordinary therapy group) and 37 normal controls. At the same time, we scored the neurologic impairment of the patients before and after the therapy. Results In cerebral infarction group, the level of plasma NO was significantly higher than the controls at 3d (P< 0.05). After 3 weeks of therapy, the level of plasma NO was not notably different between ordinary therapy group and controls (P> 0.05). While, in simvastatin therapy group, the level of plasma NO was higher than the ordinary therapy group ( P< 0.05). It was significantly different between the two therapy groups about neurologic impairment score after therapy ( P< 0.01). Conclusion The level of plasma NO in patients with acute cerebral infarction might be a reference index for cerebral ischemic damage. Simvastatin can raise the level of plasma NO and improve cerebral infarction prognosis.