Abstract: The history of the development of nuclear power system (nuclear power source,NPS) is reviewed in this paper,which contains radioisotope heater units (RHUs),radioisotope thermoelectric generators (RTGs),space nuclear reactors and nuclear propulsion systems. The use of NPS in deep space exploration and the current technical progress of NPS are illustrated in detail. Additionally,the problem of NPS safety is also discussed based on the international rules. The main technical issues and challenges of NPS are proposed when it's applied in deep space exploration missions in the future.