AMSR and MODIS are two EOS (Earth Observing System) instruments in Aqua satellite. A regression analysis between the brightness of all AMSR bands and the MODIS land surface temperature product provided by NASA indicates good correlation, and hence retrieving land surface temperature from AMSR passive data is available without ground true data (soil moisture and land surface type). The analytical results in such regions as North Africa, Northeast China, Tibet China and India indicate that the radiation mechanism of snow-covered surface is different from mechanism of other conditions. In order to retrieve land surface temperature more accurately, we can classify the land surface at least into two groups. For land surface covered with no snow, the average land surface temperature error is about 2℃ relative to the MODIS LST product. For snow-covered land surface, the average land surface temperature error is about 2~3℃ relative to the MODIS LST product. Besides, the emissivity of passive microwave is a very important parameter for retrieving soil moisture. The authors computed the emissivity through land surface temperature retrieved by the statistical regression method and made an analysis.