MODIS instruments aboard on Terra and Aqua are used to synchronously retrieve aerosol optical depth（AOD） and surface reflectance properties

and the main principles and methods to derive aerosol products from satellites are discussed in detail.The aerosol optical depth and surface reflectance over Beijing are obtained by applying the multi-channel measurements from Terra and Aqua in their different observing angles to the same surface site.The satellite retrieval results are well consistent with surface sun-photometer observations. The retrieved results of surface reflectance and aerosol ngstrm exponent are discussed by comparing them with surface measurements and literature results.Our results show that in Beijing region the reflectance radio is about 0.66 of MODIS channel 1 over channel 7 and about 0.28 of MODIS channel 3 to channel 1.Compared with the data used by dark dense vegetation background algorithm proposed by NASA for global retrieval

i.e.0.50 and 0.25 on the two channels

the final AOD results from our method are more consistent with the surface sun-photometer observations.