In this paper, the structure of mesoscale precipitation in frontalrainstorm is studied over the Jaing-Huai area is studied by using themethod of time-space change and automatic rainfall records. A conceptmodel is thus established based on the relative position of the frontalsurface and mesoscale precipitation system.The relationship between themesoscale weather system and mesoscale precipitation system is revealedthrough the analysis of the hourly ground flow field, providing thecriterion for nowcasting torrential rain.