Abstract: By using the high resolution limited area model (HIRLAM) and real data from the T106 model, the development of Southwest China vortex associated with the precipitation process over Jinfo Mountains by affection of South China Sea monsoon is simulated. The affections of South China Sea monsoon, South Asia high, topography lifting, and conservation of moist potential vorticity on the development of vortex and strong convection are discussed in detail. The results show that all these could affect the precipitation process, but here we emphasize that their properly vertical structure will play a more important role. As shown in the results, the Meiyu front is formed by the confrontation between the South China Sea monsoon and the cold air from the north in the low. When this front has been properly overlapped with South Asia high, the int ensified convection will be excited from the southwest vortex center existing in the front and causes the precipitation. But along with the more cold air from the north moving into this area in the late phase, the subtle balance will be destroyed by this motion. The precipitation stopped even if the souhtwest vortex still existed in the low.