Abstract: The ecological protection and high-quality development of the Yellow River Basin cannot be separated from the rational allocation of water resources of the Yellow River. The Yellow River runoff plays a key role in maintaining global energy balance,water and sediment cycle,climate change and ecological environment evolution. Dams strongly change the spatial and temporal distribution of water resources and interfere with the natural rhythm of rivers. Xiaolangdi Dam is China’s second largest water conservancy project,the data of Huayuankou Hydrological Station before and after the operation of the dam are sorted out by using the Range（the Range of Variability that RVA）,Theil Sen slope,Mann Kendall mutation test and methods of wavelet analysis of the degree of the change of the Yellow River runoff,amplitude,point mutation and period. The decreasing trend of annual runoff passed 99% significance test,which was the most obvious from 1998 to 2011,and the abrupt transition point appeared in 1990 and 2012. The runoff had obvious periodic changes,and the main period was lower than the contour center around 2000. The results of mutation test and wavelet analysis can predict that the annual runoff will be low in the future. During the period of water and sediment regulation,the siltation of many Yellow River sluice gate and diversion canal system is more serious due to the large amount of water,high sediment concentration and rapid water regression. The rule of runoff variation in the Yellow River is made clear,and the decision-making of dam operation management,regional territorial spatial planning and national economic development planning is adjusted,which can lay a foundation for ecological protection and high-quality development in the middle and lower reaches of the Yellow River.