Abstract: The stray light level in CCD camera is calculated with the Monte Carlo method.The comparison of the stray light coefficient of the main section from the present study with that from the experiments using integral sphere shows both the results are of the same order of magnitude.It also shows that the method and software in this paper are reliable to a certain extent.The factors causing the dissent between the calculated result and the experiment value are analyzed.So it can be said that the effect of thermophysical property parameters on the numerical simulation is significant.The analysis included the effects of the length of sunshade and the angle of reflective mirror on the stray light coefficient.The result shows that if the length of sunshade is kept unchanged,the stray light coefficient arrives at minimum and the light entry proportion is the maximum when the scan angle is 45°