Loop heat pipe radiation cooling system has good application prospects in space reactor heat dissipation due to its high heat transfer capacity, long-distance heat transfer without pump dependency, and effective isolation of mechanical vibrations. The code for analyzing the steady-state operational characteristics of loop heat pipe radiation cooling system was developed in this paper by the heat balance calculation method based on energy coupling iteration and validated through experimental results. Subsequently, the operational characteristic of the loop heat pipe radiation cooling system under design conditions and the effects of various parameters on it were discussed. It is observed that the plate-type radiation radiator with counterclockwise flow direction exhibited superior heat dissipation performance and thermal homogeneity. Additionally, the method combining surrogate models and genetic algorithm was proposed in this paper, which was used to the light-mass optimization considering the operation constraints for loop heat pipe radiation cooling system.