The thermal band 6 data of Landsat 5 is used to retrieve land surface temperature of Hefei with mono-window algorithm. The atmospheric water vapour content is high in summer. MODTRAN is used to simulate the relationship between water vapour content and atmospheric transmittance when the water vapour content is between 0.4 g/cm2 and 5.4 g/cm2. And then the simulation result and MODIS water vapor product are used in atmospheric correction and Landsat surface temperature retrieval. The uniform zone temperature is selected to compare with the MODIS temperature product. The comparison result shows that the contrast of vegetation is less than 1 K while construction is less than 1.1 K. The result can be used to atmospheric correction and then retrieve land surface temperature.