Abstract: Nitric oxide (NO), which is involved in the regulation of the cardiovascular system, nervoussystem, immune system, reproductive system, digestive system and other physiological activities, is an important biological substance with activity.Under normal physiological conditions, neuronal nitric oxide synthase (nNOS) can precisely regulate the nervous system NO production, release, diffusion and inactivation processes.But an excess of NO associates with the development of cerebral ischemia, Alzheimer's and Parkinson's psychosis nervous system diseases, while inhibition of nNOS activity can regulate the content of NO in vivo, and produce a therapeutic effect on some of the nervous system diseases.This review mainly describes the structure and regulation of nNOS and recent developments of small molecule inhibitors of nNOS.