Based on the conventional station, regional automatic station, and NCEP 1 °× 1 ° reanalysis data, the dynamic mechanisms of a heavy rainstorm in the rear of the typhoon Sura are analyzed, and terrain simulation is conducted by WRF model. The results show that the heavy rain presented obviously mesoscale features; the convergence of the low level flow field promoted the development of the ascending movement in the heavy rain area; the verylowaltitude southerly jet provided sufficient vapor conditions; the jet stream strengthened and moved northward before the heavy rain occurred. Because of the convergence line of wind speed induced by the land friction effect along the coastal area, the mesoscale heavy rain system was triggered, the strength of which had a direct impact on the heavy rain intensity.