The navigation flow conditions of canal directly impact ship navigation safety. Channel regulation measures can effectively alleviate unfavorable flow conditions. In the Pinglu Canal project, after the original channel was widened and deepened, a significant bottom elevation difference emerged between the canal and the tributaries along the original river course. These tributaries, entering the confluence with a large drop, adversely affect the navigable flow conditions of the mainstream. Xinpingshui is a representative tributary with a large riverbed elevation difference and a wide intersection angle with the canal. To ensure smooth navigation in the Pinglu Canal, we conducted fixed-bed model tests to investigate the navigable flow conditions at the confluence of the Xinpingshui tributary and the main canal. Based on the test results, we proposed corresponding regulation measures. Results indicate that, on the basis of the canal construction, widening both the main and tributary channels and installing additional dissipation pools and diversion dikes at the tributary mouths significantly improve the navigational flow conditions under various flood scenarios. The findings of this study can serve as a reference for improving navigation channels in similar river reaches.