Abstract: The former Soviet Union TOPAZ-Ⅱ reactor system used a tube-fin radiator which had single point failure problem. A heat pipe type radiator was preliminarily designed to replace the tube-fin radiator and improve the safety of the space system. According to the requirement of heat dissipation and the coolant operating temperature, the liquid-metal heat pipe with potassium was chosen, the structure materials were selected and the parameters were designed, and the structure of heat pipe radiator, the layout of the heat pipes and the copper fin were also designed. The central heat pipe steam district was modeled by one-dimensional flow equation, the heat transfer of the heat pipe wall and wick were solved using the finite element method while that of the copper fin using finite difference method. The steady state results of the radiator under designed condition were obtained by the coupling calculation of heat pipe and the transport duct. The characteristics of heat pipe radiator were compared with those of tube-fin radiator. The results show that the heat pipe radiator designed in this paper meets the requirement of the TOPAZ-Ⅱ under the normal condition and has a large margin. The isothermal and safety of heat pipe radiator are better than those of tube-fin radiator.