Abstract: In the Mei-Yu frontal cloud system. there are two kinds of meso-scale systems: meso-scale echo bands and meso-scale echo groups. Echo band consisting of convective clouds has different echo structure in different.evolution stages. Water surface and mountains have an effect on it's evolution. Analysis of precipitation shows that if several meso-scale systems pass successively through a place, or meso-scale echo bands and echo groups converge at the place, there will be local heavy rainfall. Also, meso-scale systems producing heavy rain are pf mixed cloud types, in which stratiform clouds and convective clouds coexist.