It is difficult to determine surface reflectance over bright surface. Based on the geometric optics model theory, it can be assumed that on the same day on the same ground two different band ratio approximately equal in different years. According to the history of the MOD09 blue band surface reflectance, the MOD02 seventh band surface reflectance and the MOD02 seventh band surface reflectivity, the surface reflectance of retrieval region can be obtained, and 6S radiation transmission is combined to build look-up table, to retrieve aerosol optical thickness of Beijing Area. Beijing AERONET site observations data is used to verify the outcome, the results have a good consistency with AERONET data over bright surface, and the error is less than 30%.