This study aims to clearly understand the spatial and temporal distribution characteristics, intensity and occurrence law of rainstorm in flood season in the "two mountains" region of Qiandongnan Prefecture, and improve the accuracy of forecasting and early warning of disaster-causing rainstorm in this area. Based on the relatively complete hourly and daily precipitation data from the national and regional meteorological stations in the "two mountains" region of Qiandongnan Prefecture in flood season (April-September) of the recent 10 years (2013-2022), as well as the observations from high-altitude to ground surface and the radiosonde data provided by MICAPS prediction and analysis platform on the day when the rainstorm occurred or at 8:00 on the previous day, we statistically analyze the spatio-temporal distribution characteristics, intensity and occurrence rules of the rainstorm in the "two mountains" region of Qiandongnan Prefecture in the flood season, as well as the disaster-causing rainstorm types by using statistical methods and synoptic principles and methods. The results show that: 1) The average extreme precipitation during the flood season in Qiandongnan Prefecture mainly occurs in the Moon Mountain area, while the daily extreme precipitation and maximum rainfall intensity mainly occur in the Leigong Mountain area. From May to June, the average rainstorm days in the region of "two mountains" and the average rainstorm days at a single station show an increasing trend. The rainstorm concentration period is from the first dekad of June to the first dekad of July in the Leigong Mountain area while the rainstorm concentration period in the Moon Mountain area is from the last dekad of May to the first dekad of July, about 10 d earlier than in the Leigong Mountain area. Moreover, the monthly average rainstorm days, dekad-average rainstorm days and dekad-average rainstorm days at a single station are the most in the Moon Mountain area, making this area the largest center of average precipitation in the flood season in Qiandongnan Prefecture. 2)The disaster-causing rainstorms in the "two mountains" area of Qiandongnan Prefecture are mainly the warm-sector rainstorm, cold-front rainstorm, rainstorm in the west section of Meiyu front, and tropical system rainstorm. The warm-sector rainstorm has the highest incidence and strongest intensity, followed by rainstorm in the west section of Meiyu front. The four types of disaster-causing rainstorm all occur in the context of the subtropical high strengthening its westward extension and northward uplift or weakening its eastward retreat and southward retreat. In forecasting operations, we should pay attention to the impact system while focusing on analyzing evolution trend of the subtropical high.