A persistent heavy rainfall event struck the northeast part of Sichuan and Chongqing during 2—6 September 2004. The meteorological reason and the relationship between heavy rains and the vortex in the lower-reaches of the Jialing River are analyzed. It is shown that in the east part of the Sichuan Basin, the convergence of the easterly propagating trough from the Tibetan Plateau and warm moisture from the Bengal Bay by Lower Frequency Oscillation (LFO) of the South Asian summer monsoon provides stable large-scale background and fluent moisture for the persistent heavy rains, that strongly development of meso-scale convective systems (MCSs) initiating the rainstorms and the MCSs combining into meso-α-scale vortex provides persistent lifting and available meso-scale background for lasting heavy rains, that warm advection in the lower troposphere and positive vorticity advection in the middle troposphere take advantage of the vortex development.