Abstract: With a view to improving the energy utilization efficiency of reusable spacecraft in the near space, the characteristics of flow heat transfer and entropy generation in the channel of the annular CW primary surface recuperator were investigated. Taking its heat exchange unit as the research object, the k-ε turbulent model and the periodic boundary conditions were applied to discuss the effects of the inlet parameters (i.e. the Reynolds number and temperature) on the flow characteristics and heat transfer performance of the regenerator by analyzing the velocity and temperature distributions of the outlet section of the regenerator channel. The results show that increasing the Reynolds number will reduce the temperature and increase the velocity of the outlet section of the cold and hot sides, until a central vortex is formed, which will increase the friction resistance and pressure loss of the side wall of the flow channel, thus reduce the heat transfer performance of the regenerator. The entropy generation analysis verified that, with the increase of Reynolds number, the total entropy yield increased. When the Reynolds number was constant, by changing the inlet temperature of the cold and hot sides and combined with the comprehensive changes of the surface goodness coefficient and the total entropy yield, the optimal working temperature of the regenerator can be 874.8 K for the gas inlet and 485.6 K for the air inlet respectively.