The regional heavy rainstorm on 10~14 June,2008 brought great pressure for flood Control Work to rivers and reservoirs. In this paper,the characteristics of large-scale circulation backgroundand the physical process of the southwest vortex during the occurring period of the heavy rainstorm are analyzed by using conventional observation data,FY-2C satellite and NCEP reanalysis data. The following conclusion are drawn:(1)During the period of heavy rainstorm,meridional circulation prevails at mid-high latitude circulation, there are two troughs and one ridge,which helps the cold air move southward continuously;(2)The characteristics of a saddle pattern disposition was appeared on flow field diagram at the middle and low levels.The aggregation of a large number of warm air transportation which come from the southwest flow and the inrush of dry cold air on upper levels play an important rules on intensively development and eastward moving of vortex and the occurrence of heavy precipitation.(3) The initial southwest vortex is warm,explosive warming and wetting caused by low-level warm advection increases atmospheric instability,which lead to strong upward motion and the release of condensation latent heating and the intensive development of a low vortex.(4)there are three vapor inflow corridors to the regions of heavy rains:one water vapor transmitting is belt from the Bengal Bay, and the other water vapor transmitting comes from the Sino-Indian Peninsula and the South China Sea,the third is the westerly water vapor transport.%2008年6月10～14日我国南方出现了一次区域性的强降水过程，给江河、水库的防汛工作带来了极大压力。该文利用常规观测资料和NCEP再分析资料，诊断分析了此次强降水过程发生的大尺度环流形势以及西南低涡在此次暴雨过程中的作用。其结果表明：(1)此次强降水发生期间，中高纬度经向环流明显，主要表现为“两槽一脊”型，有利于冷空气不断南下；（2）在中低层流场图上分析出了“鞍”型场的环流配置，西南地区上空低层不断聚集由西南气流输送的大量暖湿空气，而在高层有干冷空气侵入，从而导致西南低涡强烈发展、东移以及强降水的发生；（3）本次西南低涡初期具有暖性结构，暖平流使中低层增温增湿，加大了大气层结的不稳定性，从而引起上升运动和凝结潜热释放，促使低涡强烈发展；（4）影响此次强降水的水汽来源有三支：一支来自孟加拉湾的水汽输送，另一支来自中印半岛和南海的水汽输送，第三支是西风带的水汽输送。
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