Abstract: A continuous torrential rain case occurred in the south coastal areas and Pearl River delta region of Guangdong province during June 28-30, 2011. And on June 29, the heavy rain happened against the background of the monsoon surge. By using conventional observation data, data from regional automatic station and NECP/NCAR 1°×1° 6-hourly reanalysis data, the analysis is made mainly on the cause of the torrential rain affected by the monsoon surge on June 29. The results show that this process occurred against the background of the stronger monsoon trough. The breakout and increase of monsoon surge showed mainly the strengthening of low level jet. There is a good correspondence between the low-level jet and heavy precipitation temporally and spatially. The coordination between the strong convergence on the left side of low-level jet and the strong high-level convergence is one of the reasons for the occurrence and development of heavy precipitation. After the outbreak of the monsoon surge, the unstable energy accumulated again. This is conducive to the precipitation increase and maintenance.