Abstract: Based on the precipitation observations collected from the stations and the ERA5 analysis data, the moisture flux and budget of a rainstorm event that occurred in Jiangxia, Wuhan during the Meiyu period in 2020 were estimated. In addition, the Lagrangian hybrid single-particle orbit model (HYSPLIT4) is used to quantitatively analyze the contributions of various sources to the precipitation process during the event. The results are as follows. (1) The synoptic condition and its stability led to this rainstorm event and its maintenance. (2) The moisture was mainly transported from the South and West. It is the key for this torrential rainstorm event that the moisture was transported and concentrated through the Indian summer monsoon circulation at the lower latitude and the southerly flow surround the Western Pacific Subtropical High. In addition, the southerly inflow of moisture played an important role in the moisture budget of this rainstorm. (3) The main moisture sources of this rainstorm events were identified as the Indian Ocean, the Bay of Bengal-South China Sea, and the western Pacific, which accounted for 24%, 41%, and 34% of the total moisture supply, respectively. (4) The southern flow was the major channel for the moisture transport at 925 hPa, which mainly originated from the western Pacific and the South China Sea, while the southwestern flow was the major channel for the moisture transport at 850 hPa, which mainly originated from the Indian Ocean and the Bay of Bengal.