Abstract: By analysing the feature of the mesoscale activities of the storm happened in eastern part of Sichuan basin during August 30th, 2012 to September 1st, 2012, with the mesurement of Barnes bandpass filter and physical quantity method, the conclusion is the mesoscale auxiliary system matches well with the heavy precipitation position around 700hPa. Normally the strength and scope of the storm in the mesoscale vortex area with heavy precipitation is stronger and bigger than that of the mesoscale auxiliary area. This time the atmospheric convergence movement in the basin is mainly around 850hPa, which leads the mesoscale system in this storm goes stronger and maintains strong convergence or divergence movement in the whole process.The non- equilibrium state goes gradually up and then gradually down. The continued non- equilibrium vibration stimulates low- level convergence and high- level divergence develop, thus strong atmospheric rising motion accompanied.