Abstract: Extreme precipitation has an important impact on flood control and water dispatch of rivers and reservoirs.Studying the causes of extreme precipitation is a necessary stage to strengthen regional water resources management.Based on multi-source observation data and ERA5 reanalysis data，using HYSPLIT backward trajectory model and frontogenesis intensity diagnosis，the causes of a flood-causing extreme heavy precipitation in Yichang City on the night of August 26，2023，were analyzed.The results indicated that: ① In this extreme precipitation process，the low-level jet，super low-level jet，boundary layer cold air，and mesoscale vortex were the key influencing systems.The heavy rainfall period could be divided into three stages: the formation of the mesoscale vortex and the development of low-level jets，the confrontation between the cold and warm streams and the southward movement of the cold front，and the eastward movement of the vortex center.② There were four main warm and wet transport channels in the middle and lower layers of the process，which made the water vapor flux in the heavy precipitation area over 800 kg/（m·s） and PWV （Precipitable Water Vapor） over 70 mm.③ During the heavy rainfall period，the positive vorticity center and the negative velocity center basically coincided，the frontogenesis was enhanced，and the vertical ascending motion was strong，the vertical velocity at the lower level reached -7.1 Pa/s.④ During the heavy rainfall period，the θse energy front zone was formed near the terrain transition zone，the high-energy tongue was formed in the vertical direction，and the center of 800 hPa θse reached over 360 K.⑤ The combination of mesoscale topography and jet stream formed a mesoscale temperature and humidity frontal zone of “northwest cold and dry，southeast warm and wet”.The terrain played a role in blocking the uplift and triggering so that heavy rainfall appeared in the front of the mountain.The research results could provide a basis for formulating regional water management strategies during the flood season.