[Objective] The characteristics of the drought and flood in the Weihe River basin and their influencing factors under climate change were studied, in order to provide scientific support for regional water resources planning and management, ecological environment construction and maintenance, climate prediction, and disaster prevention and mitigation.[Methods] We used historical data during 1800-2017 to establish the drought and flood sequence, and the wavelet transform, sliding t-test, rolling correlation and other methods to study the flood/drought characteristics of the Weihe River for more than 200 years. And the possible causes of droughts and floods were explored.[Results] The frequency of mild droughts was the highest, while the frequency of major floods was the lowest in the past 200 years. In the first hundred years, the upper reaches of the river was dominated by drought, and the lower reaches was dominated by floods. The next 100 years were opposite to the previous ones. The fluctuations of drought and flood in the middle reaches were less. The first main period of drought and flood change was 18 years for the upstream, 62 years for the midstream, and 10 years for the downstream. Most of them were small and medium cycles. The consistency between the sliding correlation coefficient and the decrease of ENSO variance was obtained, indicating the remote correlation mechanism between the drought/flood of Weihe River and ENSO. There was a teleconnection between the drought/flood sequence and ENSO. The analysis of drought and flood period and precipitation showed that the changes of sunspot and flood period were similar in short period.[Conclusion] The mutation of drought and flood in Weihe River has a high inheritance, which is closely related to climate and environmental change. Besides, more attention should be paid to disaster prevention when the number of sunspots is low.