Abstract: In order to improve the flow pattern caused by the side wall of the narrowed Anyang River channel in the cross engineering, which is formed due to the inverted siphon culvert of Mid-Route of South to North Water Diversion Project crossly passing through the Anyang River, two kinds of side wall configuration, namely, an ellipse curve and a composite arc curve, are proposed. On the basis of the theory of hydraulics and considering the other respect requirements of the project, an optimum configuration scheme involving a composite arc curve is recommended. And through the examination of hydraulic model test, the result indicates that, with the recommended composite are curve scheme, the return flow is basically eliminated, or large narrowed and the scouring depth is reduced. So, the recommended scheme is safe, economic.