Abstract: The routine observational data and intensive observational data of "China Heavy Rain Experiment and Study-CHeRES" were used to analyze MCSs in Meiyu front during 20-24 June,2002.It was found that some MACSs produced severe heavy rainf all over middle and lower reaches of Yangtze River basin,the heaviest rainfal occurred at Huangshan station.The duration of these MCSs was longer than 10h,some of them longer than 24h.Afterwards,the MCS1 triggered over southern part of Anhui province and produced heavy rainfall was further analyzed by using intensive observational data,especialy,GPS,radar and wind profiler data.During 2021 June 2002,the Meiyu front stagnated to the north of 30°N,while shear line on 850 hPa between southwesterly along rim of subtropical high and easterly from North China located at 31°N.The Meiyu front and shear line provided favorable synoptic condition for the development of convections.In addition,the analyses show that MCS1 formed in warm-moist southwesterly to the south of shear line over Dabieshan mountain and gorge between Dabieshan and Jiuhuashan mountains.During the evolution of MCS1,two systems originated over Dabieshan mountain area and moved eastwards.The first system moved east wards quickly,whereas the second system stagnated and developed deeply.The severe rainfal occurred at rearward of MCSs.The GPS observation indicates that the precipitable water increase obviously before occurrence of rainfal about 2-3 h and decrease after it.Although the observation sites of GPS are limited,but time resolution is very high,thus,it could be employed to predict local rainfal.The wind field from wind profiler reveals that LL J extended to 4000 m accompanied the development of convection.The analysis of sounding data of 6 h interval at Anqing station captured the releasing and accumulating of CAPE during the evolution of convection.The abundant moist ure transportation by southwesterly is favorable to the maint enance of convective unstability and accumulation of CAPE.The monitoring of radar reveals that meso β and γ systems were very active in MACS and its propagation direction was not consistent with that of MACS.Several convection lines developed during the evolution of MCS1,which associated with surface convergence lines.The outflow boundary of convection line could trigger another convection line.The convection line moved with mesoscale surface convergence line,but the convective cells embedded in convergence line propagate along the line.