Abstract: With the precipitation data of 18 stations in and around Changdu from 1989 to 2018, the NCEP/NCAR reanalysis data, the heavy precipitation cases are screened firstly. Based on the classification of atmospheric circulation, the backward trajectory model is used to analyze the water vapor transport trajectory of two different precipitation levels in different circulation situations. The results show that the atmospheric circulation situation of heavy precipitation in Changdu is divided into three types: plateau vortex, plateau trough and plateau shear line. The plateau shear line type is the main type, and the plateau trough type has the largest rainfall intensity. The water vapor trajectories directions of the three isobars are basically the same when the rainstorm occus under different circuation situations, which are dominated by southerly airflow. The water vapor sources are relatively concentrated, and it is easy to cause heavy rainfall in a short time. When heavy rain occurs, the water vapor trajectories of the three isobars are mostly dominated by southerly airflow. Compared with heavy rain, the water vapor sources are relatively dispersed and the water vapor conditions are poor. In summer, the water vapor sources in Changdu are mainly from the Indian Ocean, the Bay of Bengal, the Arabian Sea and the South China Sea, which acn be traced back to the Atlantic Ocean.