The contribution of sophisticated terrain is a key factor of the generation of strong convective weather, which is hard to forecast. In order to improve the model simulation of rainfall in South China, the impact of terrain must be taken into account. A rainstorm occurred in the warm section in the southeast of Yunwushan is used as an example to investigate the simulation capability of Gravity Wave Drag by Orography (GWDO) parameterization, which is newly added into WRFV3.1, and its mechanisms. The simulation is conducted for 36 hours using the reanalysis data of NCEP (1°×1°) from 5 to 6 June 2008. Through the analysis and comparison of two experiments, it is concluded: (1) The sensitivity experiment achieved a success in the simulation of the center and strength of the rainstorm, and it revealed the largeand mesoscale circulation pattern and evolution of the heavy rain event and successfully duplicated the mesoscale lowvortex, whose temporal evolution characteristics were in accord with the movement of the precipitation center, while the control experiment without using the parameterization scheme failed. (2) The using of GWDO parameterization effectively reduced the zonal wind deviation in the middle troposphere, and the impact of terrain on the dynamic uplift of airflow was simulated reasonably. (3) According to experiments, the energy divergence in the middle caused by the orographyinduced gravity wave was the main cause of the rainstorm, which enhanced the vertical movement and made the precipitation strengthened and relatively concentrated.