As the key equipment of the starlight navigation system, the starlight direction finder is mainly used to obtain the accurate spatial angular position of natural stars, which is used for high-precision attitude calculation and navigation and positioning of missiles, ships and space satellites. Its performance largely determines the performance of the starlight navigation system. In the visible light band, the starlight direction finder is easily affected by the background radiation generated by the sun scattering in the atmosphere. According to Rayleigh scattering theory, the infrared band has a smaller scattering intensity than the visible light band, and the radiation energy transmitted through the atmosphere is strong. Practice shows that it is much more efficient to use the near-infrared band to measure stars in daytime than the visible light band to realize navigation and positioning. Therefore, developing high-precision infrared star simulator and realizing infrared star map simulation has become a new content to improve the efficiency of starlight navigation and the accuracy of star point detection. In order to realize the ground calibration of starlight director and meet the three simulation requirements of radiation uniformity, specific irradiance and spectrum, this paper proposes an optical system design scheme of infrared star simulator with uniform radiation under specific irradiance. According to the requirements of irradiance simulation and uniform irradiation, the radiation flux transfer model of light source system is established, and a uniform radiation light source system is designed to meet the requirements of radiation spectrum. According to the docking requirements of starlight direction finder and infrared star simulator, a transmission collimating optical system with high imaging quality is designed. Combined with the design results, Tracepro software is used to model the optical system, and the irradiance and uniformity of the radiation surface of the light source system and the exit of the optical system are simulated and analyzed. The irradiance and uniformity of the radiation surface of the light source are tested experimentally with an irradiance meter to verify the accuracy of the theoretical analysis. The measured results show that the irradiance of the radiation surface of the light source meets the index requirements, and the irradiance unevenness is 2.75%, which meets the development requirements of the infrared star simulator.