The circulation evolution and the convective activity of the southeast Asia region before the rainy season for Yunnan in 2001 is analyzed. The rainy season beginning of Yunnan is influenced by the summer monsoon of the BOB, the Bay of Bengal monsoon onset is earlier and stronger so that the rainy season is earlier and the rainfall is more in 2001. The seasonal adjustment and the convective activity migration to north of the southeast Asia region is an important factor to forecast the rainy season beginning of Yunnan.