Abstract: This paper presents a study of the rainfall changes at the Qingshitan reservoir (rainfall station) of Guilin using the observed data of annual rainfall and flood season rainfall, focusing on multi-time scale analysis of dry-wet alternating time scale and change point behaviors by Moelet wavelet. The results show that the annual rainfall was characterized by prominent cycles of roughly 8 years and 24 years and it tends to increase in the next three years. And the flood season rainfall took two major periods of roughly 8 years and 26 years and it will be decreasing in the next three years. The method gives an effective identification of the changes in rainfall, but its influencing factors should be quantitatively evaluated further.