A practical algorithm is developed to retrieve LST from the Multi-functional Transport Satellite (MTSAT), which was launched in 2005 by Japan Meteorological Agency (JMA). A classified Split-Window algorithm is developed under various atmospheric and surface conditions through simulations by MODTRAN 4. The coefficients in the algorithm are separated in several groups by a series of different parameters. The retrieved MTSAT LST is compared with that from Fengyun Meteorological Satellite (FY), airborne and ground observations collected in the Heihe river basin, China. The analysis indicates that the classified split-window algorithm can be successfully applied to the LST retrievals from MTSAT data.