Based on observations from the South China Heavy Rainfall Experiment (SCHeREX) and the reanalysis data from NCEP/NCAR, one kind of vortex with heavy rainfall during pre-rainy season in South China (1200 UTC 10 June－0000 UTC 13 June 2009) is analyzed, and the results are as follows. The southwest vortex (SWV) was the direct influencing system of heavy rainfall, convective activities and precipitation were always at the center or to the southeast of the southwest vortex. The rain areas moved from west to east with the southwest vortex and the short-wave trough. Convective clouds were active during this rainfall (some of them are meso-α-scale or meso-β-scale systems, respectively) and there were about 11 meso-scale rain clusters, which remained quasi-stationary or moved slowly. Neutral stratification, sometimes with thermal inversion, was located at the middle to low levels. After the southwest vortex moved out, wind at low levels changed remarkably, and the convective available potential energy (CAPE) decreased. The long persistence of cut-off low and subtropical high contributed to the stable maintenance of circulation. The short-wave trough at 500 hPa moved southward along the Tibetan Plateau, leading the southwest vortex to move southeastward to Guangxi. Influenced by the subtropical high, the trough was quasi-stationary, and after 0000 UTC 13 June, as the subtropical high retreated, the trough moved eastward. During the heavy rainfall, there were obvious interactions between middle and low latitude systems: the cold air was active, and the monsoon trough transported enough moisture to Guangxi, which enhanced the SWV. Based on the above researches, the schematic model of one kind of vortex causing heavy rainfall has been proposed.