In order to study the water level at the convex and concave banks after installing a guide wall in a spillway chute bend, with the original condition that the Fr at the entrance of the channel bend is larger than 1.0 (supercritical flow) when there is no the guide wall, systematic experiments with the guide wall were conducted for three radii (2.4B, 3.2B and 4B; B is the width of the channel), bottom slopes (0.01, 0.005 and 0.02), and discharges (50, 100 and150 m3 h−1). Results show that, firstly, after installing a guide wall, the Fr becomes smaller and even lower than 1.0, which means the flow status changes from supercritical to subcritical in some conditions with the help of the guide wall. Secondly, the water depth at the convex bank decreases with the increase of the relative axial radius while this presents to be adverse at the concave bank. Thirdly, for water surface differences in cross-sections, the maximum value decreases with the increase of the relative axial radius, and increases with the increase of the discharge per unit width or the bottom slope. Additionally, a novel formula for calculating the maximum water surface difference was obtained in this article.