The torrential rain in Chuzhou on 1 August 2008 was analysed based on the NCEP 1×1 reanalysed data ,TBB and Doppler radar data. The results showed that this heavy rainstorm process was composed of two periods of heavy rainfalls. It occurred on the background of weakening typhoon (Phoenix) circulation combined with enhancement of the West Pacific subtropical high. It was triggered separately by accretion of the southwest LLJ and the pressure trough degraded from typhoon circulation. It was caused by four MCSs. Heavy rainfall appeared in the maximal TBB gradient area of newly emerging MCS. Analysis of physical quantity and evolvement of the radar echoes showed that the interaction of the strongest moisture convergence in low-troposphere and inrush of dry cold air at middle levels was the physical mechanism of the heavy rain. The second stage of strong rainfall was caused mainly by shear line and adverse wind area appeared on Doppler base velocity and mesoscale vortex at 500hPa level.