This paper investigates the relationship between tropical circulation anomaly and the Yangtze River basin flooding in 1998.It is indicated that the circulation anomaly patterns of upper and lower troposphere in tropical western Pacific provide favorable circulation background for the Yangtze River flooding.In 1998, the tropical circulation and the convective activities in the NW Pacific warm pool region are both in the weak stage of the climate fluctuations, South China Sea summer monsoon is sustainable weak, subtropical summer monsoon is stronger.These conditions are also favorable to the more rainfall in the Yangtze River region.The mechanism of the effects of tropical circulation on the summer rainfall in China is also proposed.The relationship is applied to prediction.