Abstract:In this paper, the intensity index of current energy, which comprises flow variation-index, flow similarity-index, quotient of flow amplitudes, monsoon intensity index and flow abrupt-index, is calculated using the data, which is the output of AGCM IAPⅢ. Main conclusions are: Flow similarity-index can objectively determine the presage day of summer monsoon onset in South China Sea region. Near the day of summer monsoon onset in South China Sea region and South Asia region ,and near the day of beginning of Meiyu in the Yangtze River and the Huaihe River, the flow variation-index increase distinctly, it means that there is violent adjustment of global circulation. Climatically, the day of summer monsoon onset in South China Sea region in the model is later 10 d than real day of the onset, the onset intensity is weaker. In the model, although SST is climatic value, the presage day of summer monsoon onset in South China Sea region is different, and monsoon intensity index has distinct interannual variability of biennial oscillation. Summer monsoon onset in South China Sea region in the model belongs to almost abrupt change, which is consistent with reality.