Abstract: In order to obtain the different output illuminance of the light source used for low-light-level image intensifier comprehensive testing, the traditional light source structure and its limitation were analyzed. According to the different illuminance needed in comprehensive testing, the large-scale continuous illuminance-adjusting function of light source was studied by analyzing and improving the traditional light source, based on the diffuse reflection characteristic of the integrating sphere and the continual characteristic of the micrometer. The output characteristic of the light source was specifically analyzed. The output illuminance of 2.510-5lx～680lx and the output light uniformity of 2.3% were achieved by testing in an experiment. It shows that the light source has a large illuminance range and higher output uniformity. Therefore, it can be used in testing the image intensifiers.