Abstract: A two-level spectral model of atmospheric circulation is adopted and the physics processes of the two-level atmospheric general circulation model of the OSU is introduced in this paper. In order to investigate the formation reason of the East Asia summer monsoon, four different experiments have been performed. By comparing and analyzing of all these experiments, it reveals that: (1) the diabatic heating distribution produces weak low-level southwestlies over the monsoon region, (2) there is a mean across-equater airflow between the 45o-90oE, not in the vicinity of 105 oE and the analysis reveals that the affection of the south hemisphere is not important. (3) the mountains have played very important role in the East Asia monsoon circulation. The mechanical effect produces a low or trough on the southeast side of the Plateau, then the thermodynamic effect makes it strengthen and move close to the Plateau, thus the monsoon low or trough is formed