Abstract: An in-depth study has been made on the hydraulic roll-bending device, which is widely used in modem cold tandem mill to regulate strip flatness. Based on analyzing the relationship of some factors associated with roll-bending force such as roll profile, strip width and rolling force etc with roll-bending force, an automatic bending-force setting model for cold tandem rolling mill was developed. The model has been successfully applied to two largest cold tandem mills in China and the experimental data proved that the model is reasonable and effective.