Due to the bedrock and gravel bed of the upper reaches of the Yangtze River,the navigation-obstructing reaches are common with the diara,shoal and beach,which are of complicated boundaries.To meet the needs of the actual project and waterway regulation,there always exists a sandpit,excavation of navigation channel,the construction of the moraine dam and other ways to change the local river boundary.Taking Zhanqizi reach for example,we establish the mathematical model of the first moraine diversion dams which turn right to 0°,5°,10° respectively.The result show that the 0° moraine dam causes smaller stage rise and diversion ratio change,and it has less influence on shoals of moraine son;the 5° moraine dam has an obvious effect on the optimization of the main channel split ratio an water-ways navigable depth and flow rate,and the navigation effect is better ;and the 10° moraine dam has a remarkable effect on improving the navigation condition on the main channel,and it changes greatly the flow field,and thus causes significant river changes.The research result may serve as reference for providing a reference for the design and research of the regulation engineering of complicated navigable channel on the upper reaches of the Yangtze River.