contrast experiments are performed by diagnostic analysis on the effect of the southern hemisphere cold air activity on the northernhemisphere summer monsoon in terms of Kuo-Qian p-σ incorporated coordinate five-layered primitive equation spheric band model.Emphasis is laid on analysis of the different responses of the flow, pressure and rainfall fields as well as the dibatic heating in the Asian monsoon area, especially in East Asia, to the presence and absence of the cold air activity in the Australian area .Results suggest that the Australian cold air can make the East Asian summer monsoon enhanced and move northward, but the Indian monsoon may become weakened or interrupted. In the process the meridional wind disturbance exhibits a south north pro pagation with a time lag of ten to fifteen days.