Abstract: Based on radiative transfer model, a radiometer observation simulation system is designed, which include the effects of topography, heterogeneity, and atmosphere. The difference between simulated and measured brightness temperatures is analyzed, a sensitivity study is also carried out to assess the relative contributes of the roughness. It is found that the roughness introduces an uncertainty of 38 k. The developed simulation system should be very useful in modeling and improving our understanding of radiant mechanism.