Abstract: Riverbank erosion occurs frequently on fluvial rivers, which is one of the key issues for river regulations. The measurement of lateral erosion rate is critical for the investigation of bank erosion mechanism and revetment. A measurement system for bank erosion rate is developed based on the technology of image processing. A new method to measure the lateral erosion rate of riverbanks is proposed by tracking the location of tracing meshes on riverbanks. As a case study, the lateral erosion rate of riverbanks in an experimental channel is measured by the proposed method, and the measured data agreed with the calculated results by a semi-analytical method. Both measured and calculated results indicated that the lateral erosion rate depended on the flow velocity as well as the anti-scour ability of riverbanks. The proposed method is able to provide a technology for the further study on bank erosion mechanisms.