According to scene illumination under night sky radiation, when shooters were aiming and positioning at night, the illumination at the entrance pupil of the sight was calculated, and the generating device for infinite target simulation based on double-integrating-sphere in illumination-mode was designed in accordance with the illumination. Variable diaphragm applied to offer four switchable low light stress environments for the night vision device according to the principle of the integrating sphere, which was setting between the double-integrating-sphere. Meanwhile, for the sake of the maximum illumination could be received by the Low-Light-Level sight during the test, the installation position of the sight relative to collimator was analyzed. The results show that the three crucial factors which influenced the illumination at its entrance pupil are scilicet the clear aperture of the iris diaphragm setting between the double-integrating-sphere, the field of view of the collimator, and the installation position of the Low-Light-Level weapon sight apart from the collimator objective. Finally, the output illuminance of the integrating sphere and generating device were analyzed and calculated, the results of experiment and measuring showed that the illumination non-uniformity is<2%, which can meet the application requirements.