Cloud micro-physical structures for mei-yu front rainfall were observed by using the balloon-borne Precipitation Particle Image Sensor during June and July 1999 at Shanghai.The observations including vertical distributions of various particle size,their number density and mass density are obtained.Analyses show that icecrystals,graupels,snowflakes and frozen droplets often coexist with the liquid phase in the convective cloud clusters inbanded in mei-yu front rainband.They and their interactions play important roles in the formation and evolution of rainfall.