Abstract: Land surface temperature (LST), one of the most important ground parameter that can be retrieved from earth observation satellite data, is of great importance in studying energy flow and material exchange in soil-vegetation-atmosphere system. To acquire instantaneous LST of large area, radiation surface sensors carried by meteorological satellite platforms are often used. On board FY-3 satellite which was launched by China in 2008, MERSI is one of the sensors that can be used to get large area of LST with significant enhancement of spatial resolution to 250 m in far infrared band and leads to a higher LST spatial precision. In this paper, far infrared data of MERSI band 5 together with other MERSI hyper-spectral 1 km band data were used to calculate atmospheric transmissivity and land surface emissivity (LSE)—2 important parameters in LST retrieval. The LST retrieval algorithms were as follows. Atmospheric transmissivity which could be used to obtain water vapor content via radiation transmission model was calculated using two-channel ratio weighted method; surface emissivity was obtained via NDVI threshold method; parameters used in retrieving algorithms were improved to better suite FY-3 MERS; mono-window algorithm was used to retrieve LST. Two LST retrieving experiments were carried out in Liaoning provincial area. The retrieved products were compared with that retrieved from MODIS data using split-windows algorithm. The results demonstrate that temperature precision can reach the desired accuracy, and the spatial precision can be improved significantly.