Objective:To study the effect of gangliaside GM-1 on induced nitric oxide synthase(iNOS) after cerebral ischemic reperfusion and approach its possible mechanism. Methods:Using 2 h ischemia and 22 h reperfusion middle cerebral artery occlusion model,male SD rats were randomly divided into sham-operated group,model control group and GM-1 treat group which received GM-1 at doses of 15,30 or 60 mg/kg. The infarct size was evaluated by 2,3,5-triphenyltetrazolium chloride(TTC) staining and image assay. The NO content and the activity of induced nitric oxide synthase(iNOS) were determined by biochemical assay. Results:In comparison with model control group,the infarct size,iNOS activity and NO content were decreased in the groups receiving GM-1 at both middle and high dose except low dose. Conclusion:The rise of iNOS activity could correlate closely with brain injury,and GM-1 could reduce iNOS activity,NO connect and brain injury after cerebral ischemia.