Abstract: Nitric oxide (NO) is a small free radical molecule with the function of transfer signal in plants. A large amount of NO is accumulated in different stages of nodule development, indicating that NO performs specific signaling and metabolic functions during symbiosis. Basedon 60 literatures, the research progress of NO signaling molecules involved in different nodulation stages, the metabolism and signaling of NO in the nodulation process, and the effect of NO on symbiotic nitrogen fixation are reviewed. Meanwhile the research prospect of NO in legume symbiotic nitrogen fixation system is prospected.