The climatic features of south Asian summer monsoon are studied based on NCEP reanalysis wind data at 850hPa and 200hPa from 1958 to 1997.The results show that there exit significant differences of latitude-longitude winds in region,seasonal variations and peak style of wind over south Asian.There are two significant south-west wind centres over Arabian sea and Bay of Bengal(BOB) and their actions are different significantly.In BOB, the time of its onset and extending northward to 20°N of south-west monsoon is earlier than that in Arabian Sea while its drawback is later than that in Arabian sea,which lasts the longest in Asian monsoon.By contrasting vertical differences of winds at 850hPa and 200hPa during strong and weak monsoon years,it is found that the patterns of the cross-equatorial flow in tropics and the flow in south-Asian monsoon region are different significantly.