Through analyzing the weather situation, a local torrential rain event is analyzed in detail based on the intensity and velocity data from Doppler weather radar as well as vertical wind profilers and two dimensional wind fields derived from velocity data. It is found out that this highly convective local torrential rainfall was caused by both large-scale and mesoscale weather systems. The large-scale circulation provided abundant vapors for the torrential rain; the stratification in Bejing was very unstable, which is a necessary condition for the severe storms; and the low-level mesoscale convergence line triggered and intensified the convection.