The solar simulator can accurately simulate the collimation, uniformity and spectral characteristics of solar irradiation, it has a high simulation precision of heat flow outside space. It is mainly used for spacecraft thermal balance test, thermal coating property test and material aging test, which can effectively test the satellite's light irradiation performance and verify the spacecraft's thermal design. An integrator component is designed according to the characteristics of large and medium-sized solar simulators, which can withstand high temperature load and ensure the uniformity and irradiation energy of large and medium-sized solar simulators. The principle of integrator module of solar simulator is introduced, and the structure design, thermal design and simulation calculation of integrator module are carried out by LightTools and Flunet. The design results show that the irradiating surface of medium-sized solar simulators can reach Ф2000mm and the nonuniformity can reach ±4%. The experimental structure shows that the irradiating surface of medium-sized solar simulators can reach Ф2000mm, and the nonuniformity can reach ±3.75%, the maximum irradiance can reach 1.39 solar constants, which can meet the needs of large and medium-sized solar simulator.