Abstract: The average and anomalous fields on several meteorological elements and the features of important tropical weather systems plentiful and lean and normal mei-yu years during 1980—1992 are computed and analyzed using grid-point data from ECMWF.It is foud :(1) the mean flow and anomalous fields,maximum relative humidity and vertical motion,locations of subtropical ridge and ITCZ at 850hPa,and vertical meridional circulation and OLR field are quite different between plentiful and lean mei-yu years;(2)mei-yu intensitry relates to confluence position of southwest monsoon and cross-equatorial flow and southeast flow ,and cold air from north or northwest China intruding into mei-ye area;(3)the effect of subtropkical high on mei-yu intensity depends on the locations of its ridge line and its western ridge point;(4)there are not exact relationships between the intensities of Somali jet and southwest monsoon and mei-yu rain.