Abstract:Based on the analysis of inter annual variation of rainstorm and heavy rainstor m days in Guangxi from 1951 to 2005 with the Morlet wavelet method, it shows tha t both exist significant periodic oscillations, with strong 2 , 4 , 8 ,14 ye ar periods and 2 year period as the strongest. Moreover, the distributions of t he frequencies and intensities are so different that the short period oscillati ons are stronger than the longer ones. The rainstorm days in Guangxi exhibit an increasing tendency on a long term basis. There are four main synoptic systems that influence the occurrence of Guangxi rainstorm: tropical cyclone, southwest vortex, low level jet and upper troposphere trough, and the main influencing s ystem contributing to the excessive rainstorm in Guangxi is tropical cyclone and southwest vortex.