Based on the conventional observational data, brightness temperature (TBB) data, automatical observational precipitation and NCEP/NCAR reanalysis data, two heavy rainfall processes triggered by low vortex in the western South China during 3-4 July 2009 and 16-17 June 2008 respectively were compared and analyzed. The major conclusions can be drawn as follows: (1) The low vortex was the direct influencing system of these two heavy rainfall processes, the strong southwest jet at low levels was accompanied in the July 2009 process, but not in the June 2008 process. Mesoscale convergence may have a direct triggering effect on these two heavy rainfalls. (2) In the July 2009 process, the intensity of low level convergence was stronger than that in the June 2008 process, so was the intensity of the upward motion and warm advection, and the temperature advection lines were more dense.(3) The net transport of water vapor was more in the July 2009 process than that in the June 2008 process, as a result of the sufficient water vapor transport to the storm area by the southwest low level jet. (4) Both storm processes are closely related to the vertical circulation south of the westerly jet at the high altitude. In the July 2009 process, because of the low level, the upward motion maintains longer than that in the June 2008 process, the intensity of rainfall stronger, and its duration longer.