Using physical quantity diagnostic analysis, this paper analyzes, a MCS and the rainstorm process occurred on 7 and 8 September 2010 in the north of Jiangsu province and explores the characteristics of MCS as well as the relationship between the MCS and rainstorm process. The results show that the MCS was composed of several meso-β-scale and meso-α-scale convection clusters: in the mature stage of MCS, there was a gradual development towards the process of mesoscale convective complexes(MCC). MCS occurred in the environment with high temperature, considerably wetness and unsteady convective stratification in the air. Surface cyclone development in cooperation with the convergence and the role of the front of the uplift had provided dynamic conditions for MCS. It is also indicated that the precipitation centre corresponded with the maximum gradient of the cloud top temperature very well, so that it can provide reference for the forecast of downpour weather and its area.