The onset of Meiyu over the Changjiang and Huaihe River Basins in 2005 is late. Based on NCEP/NCAR reanalysis data,OLR data and daily precipitation data in 2005,the anomalous circulation conditions are analyzed.The abnormal activities of East Asia major deep trough,mid-west Pacific ITCZ and East Asian subtropical upper westerly jet,and their relationship with the anomalous subtropical high and cold air are discussed.The results show that the late northward-jumping of the subtropical high is caused by the exceptional deep trough of East Asia,the East Asian subtropical upper westerly jet and the weak ITCZ. Additionally,the cold wave is strengthened by the strong upper westerly jet and the subtrop-ical frontal zone is to the south of its normal location.The propagation of warm and wet summer monsoon towards the Changjiang-Huaihe River Valley is prevented by the strong cold air forcing.The late northward-shift of upper westerly jet and the subtropical high is the main reason for the late onset of Meiyu in 2005.