Abstract: With the joint operation of Sanmenxia, Xiaolangdi, Luhun, Guxian and Hekoucun reservoirs, the water-sediment process in the lower Yellow River has changed significantly.In recent years, the special water and sediment conditions have caused changes of the river regime from Sanguanmiao to Weitan in the lower Yellow River, resulting in a large number of beach collapse and endangering the safety of villages and embankments on both sides.In order to clarify the mainstream swing rule and its driving mechanism in the Sanguanmiao to Weitan reach, this paper adopted data analysis and theoretical research to describe the channel and engineering situation of the Sanguanmiao to Weitan reach, and analyzed the water-sediment process and the characteristics of the channel scouring and siltation.At the same time, according to the adjustment characteristics of the river regime in different periods and its response to the water-sediment process, the evolution trend of the river regime under different discharge processes was estimated.Studies have shown that, in the short term, the river channel formed by the long-term flood erosion was relatively stable, coupled with the the continuous improvement of the river regulation project, the probability of the river regime moving along the governing line increased.However, in the long run, with the use of the backbone reservoirs and the increase of industrial and agricultural water consumption, the possibility of continuous small flow in the lower Yellow River was high, and the mainstream swung in the channel.