Surface fluxes are important boundary conditions for climatological modeling and the Asian monsoon system. The recent availability of high-resolution, multi-band imagery from the ASTER (Advanced Space-borne Thermal Emission and Reflection radiometer) sensor has enabled us to estimate surface fluxes to bridge the gap between local-scale flux measurements using micrometeorological instruments and regional scale land-atmosphere exchanges of water and heat fluxes that are fundamental for the understanding of the water cycle in the Asian monsoon system. A Surface Energy Balance System (SEBS) method based on ASTER data and field observations has been proposed and tested in this paper for deriving net radiation flux (Rn), soil heat flux (G0), sensible heat flux (H), and latent heat flux (λE) over a heterogeneous land surface. As a case study, the methodology was applied to an experimental area at NamCo, located at the central Tibetan Plateau, China. The ASTER data of 11 June 2006, 29 October 2007, and 25 February 2008 was used in this paper for the NamCo area case. To validate the proposed methodology, the ground-measured land surface heat fluxes (net radiation flux (Rn), soil heat flux (G0), sensible heat flux (H), and latent heat flux (λE)) were compared to the ASTER derived values. The results show that the derived land surface heat fluxes in different months over the study area are in good accordance with the land surface status. The tendency is basically to maintain consistency. It is therefore concluded that the proposed methodology is successful for the retrieval of land surface heat fluxes using the ASTER data and filed observations over the study area.