Abstract: In this paper, investigation has been made into the large area heavy rain processes in eastern China. The large scale and synoptic scale vorticity field and divergence field have been calculated by the smooth filtering operator. Using deformed vorticity equation governing motions of a diverse spectrum of scale, diagnostic analysis on the characters of movement and evolution of synoptic system has been made. The results show that the filter experiment may reveal the multiple scale characters and the dynamic factors of large area heavy rain processes.