The main influential systems,various physical features and satellite im ages were synthetically contrastively analysed.Topographic features are also co nsulted.It is shown that the two torrential rain are all caused by plentiful m iosture and instability energy conveyed by the southwest airflow outside subtrop ical high,assorted with upper trough,shear line and low-level jet.The cold fron t (″7.9 torrential rain″) or development of convection at night (″7.13 to rrent ial rain″) triggered off convective instability energy and a stronger convectio n produced.Torrential rain located in the area with convective instability,high energy tongue at the middle-low level,warm advection convergence at the low lev el and divergence at the high level and ascending motion.Topographic lift and be ll-mouthed topographic effect also affected the torrential rain.