A regional-scale heavy rainfall process that occurred in the Sichuan area during 3-4 July 2012 was simulated by the Advanced Regional Eta Model, forced by first-hand data obtained from the Intensive Observation Scientific Experiment of the Southwest vortex. Results show that: (1) The distribution of the rain belt was determined by the moving path of the Southwest vortex; different initial conditions lead to a strong shift of the path in the spin-up processes, and then the large-scale circulation becomes important in regulating the movement and development of the vortex. (2) Four newly added sounding stations have impacts on all atmospheric fields; the largest differences occurred around these stations, and the largest deviations of the thermal and dynamical field were not consistent. The time series indicates that the impact of initial conditions is constrained at the beginning of the simulation, related to the model spin-up process. (3) The initial atmospheric circulation adjusted to the model spin-up process. Different initial conditions have impacts on the location and strength of the meso-small-scale vortex and forms a distinct initial state of the stable vortex. (4) The diversion, vorticity and vertical velocity corresponding to the vortex are tightly related; however, the evolutions of strength and height are not consistent.