Abstract: In order to solve the problem that how to measure solar radiation measure instrument, a kind of high precision meteorological radiation calibration system was put forward. The optimization technique of focusing system and optical integrator was described; integrator aberration which influenced the uniformity of sun simulator in detail and defocusing effect of projector lens were discussed. The optimal defocus distance formula was put forward at the same time. The collimating optical system and simulated the system in LightTools were designed. Finally, solar simulator was tested. The results show that it can simulate one solar constant with irradiation range of 200 mm, working distance of 1 000 mm. Irradiation nonuniformity in 60 mm range is less than 1%, and in(60-200)mm is less than 2%, instability is better than 1%/h, which meets the requirements of meteorological radiation calibration system.