As one of the core components of electric vehicle, the performance of power battery is largely determined by thermal management system. Air cooling is difficult to meet the heat dissipation requirements of high-power power batteries. Liquid cooling arrangement is complex and requires high sealing performance. Phase change materials will increase the mass of battery packs. Heat pipes have good heat conduction, temperature equalization performance and light weight, and it is an ideal cooling and heat dissipation technology with efficient cooling fins. In this paper, a thermal management system of power battery based on heat pipe and fin is proposed. The maximum temperature and wall temperature difference of power battery are reduced by heat pipe and fin heat dissipation. The influence of different fin spacing and heights on the thermal management system is studied, and then the fin spacing and height are optimized. The models of battery heat generation and heat transfer, heat pipe heat transfer and fin heat dissipation are established. The heat dissipation effects of fins with different spacing and heights are analyzed. The fin spacing and height are optimized according to the maximum temperature of battery surface, the temperature difference of battery wall and the total mass of fins. Finally, the temperature control effect of the heat pipe-fin thermal management system is simulated under different environmental temperatures and different discharge rates. The results show that the total mass of the optimized fins is lower, and the thermal management system has a good control effect on the battery temperature. When the fin spacing is 6mm and the height is 22mm, the total mass of the fins is reduced by 39.43%, and the battery temperature can be controlled within 321K, and the temperature difference between the cell walls is less than 3 K. This study has certain reference significance for battery thermal management technology based on heat pipe-fin, especially optimizing the thermal management system by integrating its effect and weight, which can provide a new idea for thermal management of power battery.