Abstract: Side weirs of simple structure and high accuracy are usually installed along the side of main channels to spill and control water flow. Convenience and economic benefit in application could be achieved by combining their roles in flow rate measurement and flow division. In this study, we have conducted a laboratory experiment of trapezoidal sharp-crested side weirs of different crest angles (0°, 3°, 6° and 9°) in a rectangular channel under different discharges, and analyzed their flow characteristics and influencing factors. For different crest angles of side weirs, water surface profiles were measured and flow division ratios were calculated, and relationship of discharge coefficient versus influencing factors was examined. Results show that the flow division ratio at a fixed crest angle increases with the increasing inflow rate and the variation range of flow division decreases with the increasing crest angle. A flow division formula of high accuracy with a correlation coefficient of 0.921 was obtained. We also formulated a discharge coefficient formula by adding two inflow parameters of P/h1 and Fr1 and achieved a relative error of less than 8.1%, meeting the accuracy requirement of practical measurements. This work is a preliminarily study on the combined roles of flow rate measurement and flow division and it would provide a new direction for further study on side weirs and their engineering application.