Abstract:  Payload of QUESS is sensitive to space background light. During payload testing, the time intervals should be singled out beforehand in order to make a successful QUESS payload calibration. Background light is mainly due to the Earth, the Moon, and so forth. QUESS orbiting in space, its relative positions varies with respect to the positions of the Moon and the Earth. To prevent from pollutions of background light, some time intervals should be carefully singled out during the QUESS payload calibrations. Therefore, some time intervals are simulated suitable to make QUESS payload calibrations. It has shown that such a research has led to much successful QUESS payload calibration inorbit, which is key to QUESS experiments in orbit.