Abstract: The construction of the Three Gorges Reservoir may brings about a new problem to the Lujiahe shallow reach,and chamfering the Shihong(the right thalweg)is one of the measures suggested Based on the model experiment,the effect of chamfering has been studied,proving that chamfering can solve the problem of lag in depth in the navigation channel of shahong(the left thalweg)and escarpment and riffle as well,and improve the navigation condition of the whole reach completely Meanwhile,chamfering will make the main flow translocation with the lateral branch in dry season,and decrease the discharge diverting ratio of the Songzihe River(an important tributary of the Yangtze River in this reach)from the Yangtze River,etc However,the extra descendent of water stage of the upper reach resulted by the chamfering may foreclose the normal navigation condition of the Gezhouba Ship Lock,etc.