Abstract: Mountainous areas in Southwest China are very complicated.The sudden rainstorm and its induced flash flood are the main types of mountain disasters in Western China.At present, one of the important reasons for the low forecast level and insufficient ability of sudden rainstorm in Western China is that the influence of mountain on rainstorm and its outburst is not considered effectively, and the guidance of formation and development theory of mountain sudden rainstorm is lacking.This paper summarizes the important progress in the research on the characteristics and mechanism of mountain torrential rain, which was rarely seen in the past, under the support of the national key R & D program.The basic characteristics and environmental conditions of mountain sudden rainstorm and related mesoscale convective system in Western China, especially in Southwest China, and the multi-scale and multi-level influence system of mountain sudden rainstorm are discussed.The results show that there are different effects of creeping flow and circumfluence caused by topography on sudden rainstorm in mountainous area, the possible influence mechanism of coupling effect of inertial gravity internal wave and convection on sudden rainstorm in mountain area, and the comprehensive effect of double low-level jet stream on mountain sudden rainstorm.In the end, several research directions and breakthrough points that need to be strengthened in the future are analyzed and prospected.