Abstract: In this paper, the Eulerian method is used to analyze the water vapor transport and its anomalous characteristics in three persistent rainstorms in the northeastern part of the basin in summer. The main water vapor transport channels affecting northeastern Sichuan are then simulated using Lagrangian trajectory model. The results show that:(1) The enhancement of water vapor transport by multi-system interaction at different latitudes is an important cause for the abnormal water vapor intensity of two persistent rainstorms in 2007 and 2010. In the case of the persistent heavy rain in 2012, the abnormal water vapor mainly originates from the interaction of the two vapor sources in the Bay of Bengal and the South China Sea. (2) The source of water vapor can be traced back to the Bay of Bengal, the South China Sea, the Western Pacific and the Arabian Sea. Water vapor transport in boundary layer is primarily from the South China Sea along the Southern China area in northeastern Sichuan Basin. The water vapor transport path in the lower and middle layers is either the Bay of Bengal to the northeast of Sichuan, or the South China Sea to the northeast of Sichuan, or both. During the persistent rainstorm, the superposition of several water vapor transport channels in the vertical direction promotes the strong water vapor flux in northeastern Sichuan. (3) Each water vapor transport channel has different functions in different events. The water vapor transport channel in the same event is not fixed, and different rainfall stages correspond to different water vapor transport channels.