Abstract: The radiance reflected from neighboring slopes is calculated with an empirical Lambertian model.An assessment model is developed to analyze relative error of target reflectance when neglecting incoming irradiance is neglected from surrounding terrain which will cause the reflectance of target pixel to be overestimated.The overestimation of reflectance will be stronger in shaded areas,which could bring more saturation value in topographically corrected image.The results show that radiance reflected from neighboring vegetation in near-infrared spectrum and neighboring snow in the visible and near-infrared spectrum should be accounted when we compute the reflectance of targets.Especially in the case of deep valleys,the overestimation of target reflectance could be more than 10% when the radiance is neglected.