In this paper an algorithm used to derive the aerosol optical thickness over land is developed. The algorithm is based on a Look-Up Table of the up surface reflectance computed from the 6S model and requires that some pixels in the image will correspond to the dense dark vegetation as the surface cover. The aerosol optical depth is computed by interpolation from the Look-Up Table automatically. The algorithm was applied to the middle area of Jiangxi. The average aerosol optical thickness derived from the imagery shows a good agreement with measurement from the observatory.