Abstract: In order to calibrate and test the space object cameras and star trackers, a starlight simulator which can simulate the minimum objects at infinite distance and the light source with weak starlight illuminance is required. In this way，the space object camera and star sensor can be calibrated in the laboratory and the effect of atmospheric variation can be reduced. The starlight simulators are made of the integrating sphere uniform point source and collimator, which can adjust the dynamic range of the light energy with iris diaphragm, raise the simulation star magnitude, detect the illuminance of point sources accurately, and then solve the problem of calibration under the condition of weak light by precisely measuring all the factors which influence the-illuminance of the star magnitude. The performance and accurate of the starlight simulator are analyzed. It meets the requirement of calibration and test for the space object camera and star trackers in the laboratory.