During irradiance regulation with solar simulators, narrow regulation range, discontinuous values, and other defects seriously affect irradiation instability and spectral matching. Therefore, a method based on the theories of ring concentrated light and symmetric uniform light is proposed for solar irradiation modulation. Firstly, the energy distribution of the irradiated surface formed by the light distribution with an ellipsoidal mirror is studied. Subsequently, the energy modulation method based on through holes is proposed by studying the uniform light mechanism of optical integrators. The irradiance distribution function is combined to obtain a uniform irradiance distribution. Finally, the irradiation regulation system is designed, which continuously adjusts the irradiance by changing the aperture size of the irradiation regulation plate, and the irradiance is simulated with Lighttools. The simulation results show that the irradiance of the solar simulator is continuously adjustable in the range of 490.38--1473.78 W/m ², and the nonuniformities under different irradiances are better than 1.76% (meeting the requirements of Class A in the calibration specification of solar simulators) when slope error of ellipsoidal mirror is σ=2 mrad. In conclusion, the wide-range irradiance regulation of solar simulators is realized, without changing the irradiance instability and spectral matching.