In recent years the satellite monitoring capabilities in particular to derive maps of aerosol optical depth (AOD) have increased tremendously. There are many aerosol retrieval algorithms for different satellites and sensors such as Dark-Target method (DT), Deep Blue, etc. In this paper, we used an improved approach called the Synergetic Retrieval of Aerosol Properties (SRAP) method to retrieve aerosol properties over land surfaces by using the MODIS data. The improvement of the SRAP method include the following respects: 1) Considering the importance of gas absorption correction, we use ancillary data acquired from National Center for Environmental Prediction (NCEP) analyses to correct the effect of gas absorption. 2) A new cloud mask based on a spatial variability test as well as the absolute value at the 0.47 µm and the 1.38 µm bands were implemented in the SRAP algorithm.