Abstract: Using conventional observation data and ERA5 reanalysis data, the circulation background and main precipitation mechanism of a persistent heavy rainfall weather process in northwest Yunnan from March 31 to April 7, 2022 are analyzed. The GDAS data and HYSPLIT model were employed to simulate the backward trajectory of air blocks in different high layers during the precipitation process, discussing the contribution rates of different water vapor transport channels. The results show that: (1) The cold air from high latitude constantly pushed to southern region and the Western Pacific subtropical high strengthened in west, the southern branch trough remained steady. the southwest air and the southerly air flow established a stable water vapor channel. The effective configuration of the high and low altitude systems and strong water vapor convergence were the main reasons for the formation of this sustained heavy precipitation. (2) The 500-hPa westerly jet, 700-hPa southwest jet, and the 850-hPa southerly flow provided sufficient water vapor for the rainfall process from the Arabian Sea, the Bay of Bengal, and the South China Sea. Water vapor convergence was evident, and the region of high moisture flux coincided with the heavy rainfall area. (3) The Dulongjiang Station was mainly affected by water vapor transport from the South China Sea, Bay of Bengal, Arabian Sea, and Caspian Sea, with contribution rates of 14.3%, 77.2%, and 8.5%, respectively. while the Gangfang Station was affected by the water vapor transport from the Bay of Bengal, Arabian Sea, and Caspian Sea, with contribution rates of 86.2% and 13.8%, respectively.