Abstract: With introduced physical processes from OSU's 2-level grid model, an 2-level spherical spectral model developed by the institute is used to simulate the summer monsoon circulation in the Southeast Asia and the South China Sea in May. Experiments of comparison between the presence and absence of mountainous topographic effects suggest that the topograph plays an important role in the establishment of the summer monsoon circulation in East Asia and the formation of precipitation and atmospheric heat sources in the monsoon region.