Abstract: In order to reflect the flood control situation of Weihe River, based on the data of hydrology, sediment and river topography from 2002 to 2020, through data analysis and numerical calculation and other methods, the characteristics of water and sediment variation, river erosion and deposition and influencing factors in the lower Weihe River of Sanmenxia Reservoir were analyzed. The results show that: The flood magnitude and field frequency above 1000m³/s at Lintong flood peak of Weihe River showed a decreasing trend since the prototype test; Xianyang and Huaxian Stations are normal water and dry sand series. The accumulative erosion sediment is 266.3 million m³ in the lower Weihe River, and the cumulative siltation amount changed from gradually increasing before the prototype test to gradually decreasing. The water and sediment condition of Lintong station is an important factor for the erosion and silting between sections 13 and 26. There is a positive relationship between the variation of accumulative siltation volume in Weiyu section below 13 and elevation rise and fall of Tongguan after flood seasons, and the correlation coefficient is 0.82. Some suggestions are put forward, such as to strengthen the planning and construction of river regulation and the management and defense of existing projects, further reduce the Tongguan elevation, and strengthen the comprehensive benefit of reservoirs and comprehensive utilization of water resources.