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.