Based on the Morlet wavelet transform and R/S method, the evolution features of the 55 years annual withered runoff in Guilin hydrometric station of Lijing River was analyzed. The results showed that the lowest runoff have primary period of 12 years and 30 years and subperiod of 4 years and 6 years, which represented the period change. The annual lowest runoff showed the tendency of dropping off and the 6, 12, 30 years shared the same tendency. 4 years showed the tendency of increasing. Meanwhile, P-Ⅲ was used to calculate the minimum frequency of every period. The frequency of the lowest runoff(8.09 m³/s) for 4 years was 35%~40%, the frequency of lowest runoff(5.3 m³/s) for 6 years was 10%~15%, the frequency of lowest runoff 10.2 m³/s for 12 years was 55%~60%, and the frequency of lowest runoff(3.8 m³/s) for 3 years was 1%~5%.