Abstract: In deep space exploration, due to the inability to use solar power or solar energy utilization efficiency is too low, space nuclear power is needed. So far, the isotope radioisotope decay energy is mainly used for nuclear power deep space explorers exploring the Lunar surface, Mars surface, Jupiter and beyond , while decay heat energy is used for temperature control and thermoelectric power generation. The applications of space nuclear power in deep space exploration include the Lunar base project, manned Mars flight, unmanned exploration and so on, where the fission energy is adopted. The reactors used in space fission power include reactors include liquid metal cooled reactor and gas cooled reactor. The former is able to support thermoelectric, stirling and brayton power generation, while the latter is able to support brayton and MHD power generation. The deep space explorers with the fission power attract much attention recently. From the perspective of the development of space nuclear power, the radioisotope thermoelectric generator will still play an important role in this field, and large space nuclear power combined with electric propulsion system will be an important direction of future deep space exploration.