Base on the constraint conditions of rolling temperature, rolling force, rolling torque and motor power, a constraint model of the smallest permissive rolling thickness for hot continuous rolling was established. Based on the limiting condition of optimal shape and aiming at the optimal object of relative equal load, a model of optimizing rolling schedule was established. Through the calculation and comparison, it is found that not only the optimized rolling schedule could guarantee a good shape of plate, but also the relative equal load distribution could fully play the ability of rolling mill and motor so as to calculate the minimum rolling thickness more accurately. According to this method, the simulation calculation program for permissive rolling range of products was developed under different widths and thicknesses. Therefore, this program has a high accuracy by comparison, and it could accurately reflect the rule of permissive rolling range of different steels. For a rolling line, when the product is wide, the minimum rolling thickness is mainly limited by the rolling force, rolling torque and other constraints. However, when the rolled workpiece is narrow, the rolling mill force parameter is rich, and the minimum rolling thickness is mainly limited to the finish rolling temperature.