This article introduces a new method for mutation detection, the approximate entropy method, which is based on the complexity of time series. The mutation of average annual sediment discharge in Wu Jiang River Basin from 1960 to 2016 is detected by the introduced approximate entropy method, and compared with the results of double cumulative curve method and B-G segmentation algorithm. The mutation physical mechanism of the sediment discharge is discussed from the aspects of sediment source, annual distribution and interannual variation, climate change, impact of water conservancy and water conservation projects on sediment transport. The results show that mutation points occurred at 1984 and 2008 at Wu Long station, and the sediment discharge has a significant change after 2008. The mutation of average annual sediment discharge in Wu Jiang River Basin is caused by both climate change and human activity. Sediment reduction effect of the hydraulic engineerings built since 1990s climate is main and direct, and the climate change have secondary effect on sediment discharge change.