Abstract: A systematic experiment on a round head pier for measuring the flow in a U-shaped channel has been conducted for the cases of six channel slopes, six flow contraction ratios, and three pier aspect ratios, focusing on the effect of channel slope on the hydraulic performance of the pier and its applicability to the irrigation areas in North China. We analyzed the water surface profile and the pier shape suitable for different channel slopes, and examined the slope effects on the backwater and head loss of the pier, upstream Froude number, and critical submergence. A concise, practical discharge formula of high accuracy was obtained by fitting the experimental data. The test results show that when channel discharge, contraction ratio and aspect ratio are fixed, a reduction in channel slope leads to an increase in the depth and distance of backwater and a decrease in flow head loss and upstream Froude number. A negative correlation exists between the channel slope and the contraction ratio or aspect ratio of the pier. The round head pier has a great critical submergence of relative degree 0.90.