Analysis of a heavy rainfall event at Cangzhou, Hebei Province 11-12 October 2003 is made from some aspects such as influence systems, triggering mechanism, stability and physical quantity fields, etc. It shows that the event belongs to stable rainfall, its energy accumulation is smaller than that in summer, but the jets are stronger with the high value center of the mid-low level convergence and the upper-level divergence and playing an important role in the formation of the event, providing vapor and motive terms, and the heavy rain region appears with the high value center of upshift velocity.