Utilizing Landsat TM/ETM+ and Terra ASTER data, the authors retrieved the land surface temperature (LST) of Beijing during the summer of 1990~2007, and analyzed the spatial distribution and temporal variation of LST in the study area. The retrieval of LST from Landsat TM/ETM+ data applied the generalized single-channel method, while split-window algorithm was introduced to the retrieval from ASTER data. The LST data were converted to histogram equalized maps and then synthetically compared and analyzed. Spatial distribution of LST in the summer of each year as well as the temporal diversion was summarized. It is thus known that the Heat Island Effect has been mitigated since 1999. In the end, the shortcomings in the achievements are analyzed, and the orientation of future work is pointed out as well.