Abstract: Using rainfall hydrological data from 17 hydrological stations in the Yishu River Basin from 1990 to 2024, different scales of drought flood transition indices were constructed. Mann Kendall trend test, rescaling range analysis, Pettitt mutation test, and Morlet wavelet analysis were combined to detect the long-term trend changes of drought flood transition indices, analyze the persistence characteristics of drought flood transition indices, identify the time series mutation points of drought flood transition indices, and reveal the periodic variation characteristics of drought flood transition indices. An in-depth exploration was conducted on the characteristics of sudden changes in drought and flood during the flood season in the watershed. Research has found that in the future, the phenomenon of "flood to drought" will dominate in long cycles, while in short cycles, the phenomenon of "flood to drought" will increase in June to July and August to September, and gradually increase in July to August.