Abstract: In this paper, the preliminary design and analysis of the heat pipe radiation radiator for space reactor were carried out. The heat transfer model of a single radiator plate was established, including the convective heat transfer between the coolant and the evaporating section, the heat transfer from the evaporating section to the condension section, the heat transfer between condensation section and C-C cladding, C-C cladding heat radiation and so on. Five different proposals were calculated, which shows the variation of coolant temperatures along the flow direction. The results show that when the number of heat pipe is 7 436, the design requirements are met. In the case of a fixed number of heat pipe, the optimal fin width of the radiator is 30 mm, and the appropriate coolant flow rate of the single radiator plate is 0.5 kg/s.