Abstract: On July 4, 2023, an extreme rainstorm process occured in the north of Enshi Tujia and Miao Autonomous Prefecture (hereinafter referred to as Enshi Prefecture) in Hubei Province. A regional heavy rainstorm occured in the north of Jianshi County and Badong County. Among them, an extremely heavy rainstorm with an hourly rainfall intensity of 116.8 mm and an accumulated rainfall of 320 mm in just 5 hours occured in Changliang Township of Jianshi County, causing serious disaster in the local area. By using the conventional high altitude and ground live monitoring data, combined with satellite, Doppler weather radar, and the reanalysis data of the European High Resolution Meteorological Center (ECMWF), the weather situation background, mesoscale environment, and the occurrence and development process and mechanism of rainstorm mesoscale convection system in this process are analyzed to reveal the cause of extreme rainstorm. The results indicate that: ① The "two troughs and one ridge" in mid to high latitudes, the development of precipitation systems in the westerly belt, and the stability and moderate location of subtropical high pressure in low latitudes are favorable large circulation backgrounds for the formation of heavy precipitation; ② The development of the southwest vortex led to the strengthening of the warm and humid air flow in the southwest before the vortex, which promoted the surface frontogenesis. In addition, the convergence and uplift of the terrain in Southwest Hubei Province formed the strong convergence of the mesoscale vortex shear, which is an important reason for the local extreme rainstorm; ③ The mesoscale environmental conditions show more extreme characteristics, such as high energy, strong upward movement, high precipitation rate, etc., which play an important role in stimulating the mesoscale convective rainstorm; ④ In the north of Enshi Prefecture, the influence of a backward propagating mesoscale convective system appears, while the "inverted bell mouth" topography leads to the countercurrent of the thunderstorm cold pool, and forms a stable mesoscale convergence upward movement with the environmental wind, which makes the precipitation highly concentrated, which is the key factor leading to the formation of extreme rainstorm.