A meso-scale heavy rainfall occurred in the Yangtze Hui River Basin during July 4—5 2003 was simulated by use of the non-hydrostatic meso-scale model MM5 (V3-6). The main results show that, in the well developed convective cloud, ice, snow and graupel concentrate at a specific level around 200 hPa, 300 hPa and 400 hPa respectively. The difference tendency of ice particles is consistent with that of simulated rainfall, while the difference of spatial distribution gradient of simulated rainfall may be reflected by that of graupel. So it is critical and mostly to be the main factors to well simulate the regional spatial distribution of the integral ice phase coagulations for a good simulation of the distribution of rainfall. The evolution types of density of snow and graupel are consistent with that of ground precipitation very well. The collection process of cloud water with ice is the most important cloud micro-physical process that brought about the heavy rainfall.