Abstract:The torrential rain events in North China include regional or valley torrential rain and also contain local torrential rain only covering the area of several hundreds to thousands square kilometers. Essentially, these torrential rain events all result from the interaction of multi-scale synoptic systems with diversity of dynamical structures. However, it is not easy to clear up the interaction processes of every torrential rain event. From the views of the multi-scale synoptic systems and their interactions, the paper sums up the main mechanisms of torrential rain in North China by reconstructing interrelated research achievements. The findings are as follows. Synoptic scale systems act as controlling functions in large-area torrential rain events. Their dynamic properties constructed by various essential factors play leading roles on large-scale moisture convergence intensity, the ascending motion strength and the duration. As far as the rainfall intensity and the location of extreme precipitation during a torrential rain event are concerned, the mesoscale systems are decisive factors. They are possible to be derived from the interaction of synoptic scale systems, induced by the complex underlying surface such as terrains, urbans and interface between land and sea, and engendered by feedback effect of local severe precipitation. For the extreme precipitation intensity during torrential rain events over North China, the generation, development, structure evolution and organization of deep convective storms are the key factors. The exceptionally complex nonlinear interaction processes exist in torrential rain events over North China by various interactions among the different-scale synoptic systems and complex underlying surface forcing. It is actually difficult to separate any unitary system or isolated dynamical process perfectly from the complex interaction whether by actual observed data or by numerical simulation. In other words, the complex nonlinear interaction process itself is a weather life system built by diverse feedbacks to each other. Some scientific issues on torrential rain events in North China, which should be resolved in future, are discussed in last part of the paper.