By using the hourly GMS infrared imagery and conventional meteorological data,an analysis of the heavy rain over Huabei plain and the east of Northwest China during 3-6 August 1993 is made. It is mainly to inquire into the problems with the genesis and development of the meso-α-ascale convective systems which caused severe convective weather. The results shown that the envirinmental conditions,especially the interaction between the cloud system of the middle and low latitudes for the formation of large cloud clusters is very important. The negative area of the wetbulb potential temperature is helpful to the prediction of the emergence of heavy rainfall.