Abstract: Through analyzing the change of south Asia high character index and upper air trough,the impact of South Asia High on Jiangsu plum rain and main precipitation area are discussed.Together with 15 years of South Asia High character index,the distribution of South Asia High character index in different plum rain patterns are studied.In the meantime,using altitude field data from 2002 to 2005 and 45 years of NCEP data on 100 hPa,the 100 hPa circulation difference of different plum rain patterns is analyzed.Some results are gained.(1) There is close relation between the change of south Asia high character index,trough in the westerlies and plum rain date character(the beginning,ending dates and lasting days of plum rain,rainfall and area of rain).(2) The total circulation field on 100 hPa and average character of South Asia High have some links with plum rain duration and plum rain type.The average values of South Asia High ridge line and eastward advancing index in June and July and during the plum rain have some indication for the forecasting plum rain intensity index.