For the navigation flow conditions，there are many challenges to be faced in a ship lock reconstruction and expansion project at a sharp-bended river reach. In case of the reconstruction and extension project for Shanxiu lock on the Zuojiang River in Guangxi province，flow conditions in the approach channels of various design schemes are analyzed and compared by using the two-dimensional flow mathematical model. The results show that comprehensive measures such as reasonable excavation for the convex bank，and layout of concave bank submerged dam and guidance wall can effectively improve the navigable water flow conditions.