In order to improve the performance of a solar simulator to measure the characteristic parameters of solar cells more accurately,how to control the radiation parameters for the simulator lamp was studied,such as the radiation utility rate,radiation uniformity,radiation intension,radiation stability,and so on.A coaxial optical system was selected as the optical system of the solar simulator.Then,the utility rate the lamp radiation and radiation uniformity were improved by ameliorating the optical system structure layout and increasing an optical integrator.On the basis of analyzing the existing control circuit of the simulator,an optical feedback technology was adopted to redesign the control circuit and to improve the control ability on radiation intension and radiation stability.The experimental results indicate that the new solar simulator can effectively control radiation intension and stability.When the standard light intension is 1000 W/m2,the radiation uniformity is 2.5% and the radiation stability is less than 1% in a diameter of 250 mm,which has greatly improved the performance of the solar simulator.