Based on the Mantingdashaba Wumingzhou regulation scheme of the Lancang River class IV waterway construction project，this paper expounds the general situation of waterway hazards and the characteristics of navigation obstruction. Considering the impact of sand mining on the waterway conditions and waterway regulation in the bend shoal reach，the changes of channel conditions before and after sand mining and the expected effect of the original recommended scheme are analyzed from the aspects of water level，velocity，gradient，beach elimination index，etc. It is believed that sand mining will bring adverse effects on the stability of dredging navigation channel and the ship’s self-propulsion on shoal the beach. Some measures are proposed，such as adjusting the regulation buildings to guard the navigation channel，harnessing water to attack sand，adjusting water surface and gradient distribution，etc.，in order to improve the hydraulic condition of the waterway and maintain the stability of the navigation channel after dredging. The conclusions are as follows：1） Sand mining will have adverse effects on the waterway conditions and waterway regulation of the shoal reach. 2） To ensure the waterway conditions and the effect of waterway regulation，it is necessary to adjust the layout of regulation buildings to solve the new problems of navigation obstruction.