Objective To investigate the influence of the nitric oxide synthase(NOS) in the sympathetic nervous system on proliferation of vascular smooth muscle. Methods The model of proliferation of vascular smooth muscle was established by injuring common carotid artery by FeClSUB>3/SUB>.Twenty-four SD rats were divided into 4 experimental groups：sham operation group, survival 1 day group，survival 5 days group and N-nitro-L-arginine(LNNA) treatment group. Cervical sympathetic ganglion and spinal cord intermediolateral nucleus were retrogradely labeled by injection of 3% fluorogold(FG) into carotid sheath and cervical sympathetic ganglion, and nicotinamide adenine dinucleotide phosphate diaphorase(NADPH-d) reactivity was detected histochemically. The proliferation of vascular smooth muscle was observed by hematoxylineosin(HE) staining. Results Compared to sham operation group， NADPH-positive neurons of cervical sympathetic ganglion and spinal cord intermediolateral nucleus were increased in survival 1day and 5 days group,especially 5 days group，but decreased in LNNA group.The proliferation of vascular smooth muscle was significantly increased in LNNA group as indicated by HE staining. Conclusion The NOS of the sympathetic nervous system plays an important role on proliferation of vascular smo