A pre-swirl turbine disk structure is proposed to solve the problems of excessive temperature and large temperature gradient of the turbine disk surface of space nuclear power spacecraft. The surface heat transfer characteristics of turbine disks with or without the pre-swirl cooling structure are analyzed by numerical simulation， and the influence of the rotational Reynolds number on the heat transfer effect is studied. The results show that the pre-swirl structure can effectively improve the convective heat transfer coefficient of the helium-xenon cooling air flow and the turbine disk， and reduce the maximum surface temperature and temperature gradient. The maximum temperature with the pre-swirl structure is 63.1 K lower than that without the pre-swirl structure. With the increase in the rotational Reynolds number， the maximum temperature of the turbine disk surface decreases， while the average heat transfer coefficient of the turbine disk surface increases. The average heat transfer coefficient with the pre-swirl structure is 13.4% higher than that without the pre-swirl structure.