Abstract: Two samples of mesoscale convective system (MCS) were selected for study, the structure of the rainfall and the characters of radar reflectivity at 6 km altitude were analyzed. The relationship between the characters of the radar reflectivity at 6 km altitude and the lightning characters was given. In the MCS at the new born to developing stage, the ratio of the area of the convective rain to the stratiform rain is larger than that of the MCS at the mature to dissipative stage. The ratio is only 0.15 of the MCS2, indicating large area of the stratiform rain. Three-dimensional rainfall structures of the two samples of the MCSs indicated that the shapes of the radar reflectivity of the conv ective rain were looked like columns, and that the altitude of the radar reflect ivity height of the convective rain was obviously higher than that of the strati form rain. It was always more than 10 km high. The radar reflectivity of the stratiform rain was relatively lower and broader. Generally, it was not higher than 6km. Furthermore, the relation between the radar reflectivity and the charact ers of lightning was discussed. The result showed that most events (one kind of lightning data) occurred between 20 and 45 dBz, which corresponded to the area of the convective rain and part of the stratiform rain. Distribution of the events was different in developing stages of MCS. In the MCS at the new born to devel oping stage, the number of the events was relatively small. Most events occurred between 25 and 45 dBz, corresponding to the area of the convective monocase in the MCS. In the MCS at the mature to dissipative stage, the number of the events was relatively large. Most events occurred between 20 and 45dBz, corresponding to the area of the convective rain and the transition area of the convective cloud to the stratiform cloud in the MCS.