Abstract: The extreme rainstorms in Sichuan with steep terrain characteristics has always been difficult to forecast, not only because of their destructive nature, but also because they often induce secondary disasters such as floods, flash floods, mudslides and landslides. In this paper, the studies of recent research on extreme rainstorms in Sichuan are summarized, and the observation, mechanism, and early warning and forecasting techniques are reviewed. It is concluded that the extreme rainstorms are mainly related to the activities of Mesoscale Convection Systems (MCSs), and the mechanism of rainstorms varies in different regions, among which the extreme rainstorms in the western part of the Basin are related to the control mechanism of the double-secondary vertical circulation, while the extreme rainstorms in the eastern part of the Basin are related to the large helix caused by the development of mesoscale eddies or vortex-vortex coupling. The extreme rainstorms in Panxi area are related to the dynamical topographic shear formed by the northeasterly winds of the Basin and the warm-humid southwesterly airflow near Liangshan. In terms of forecast and warning techniques, due to the support of satellite, radar and high-resolution numerical models, as well as the improvement of various forecast revision techniques, the level of extreme rainstorms in the complex terrain of Sichuan has been significantly improved, but the quantitative forecasts with 100-metre resolution still need to be strengthened.