An energetic diagnostic analysis for the heavy rain process caused by typhoon Saomai is made in this paper. It is revealed that a ridge located in Shanxi Province at that time is the mainly large-scale circulation system of No.0608 typhoon saomai. The northwest air current in front of the ridge steers the cold air from polar region continue moving southward, which favors the cold and warm air effect one another in the eastern China. Plenty of vapour and the effect between cold and warm air benefi...