In tandem cold mill, a strip is flattened by stands of rolls to a desired thickness. In the process, there exists thickness disturbance and hardness disturbance, which will affect the export thickness of the strip. In order to solve these problems, control system adopt a new control strategy wherein a state-dependent Riccati equation is utilized. In the third part of this paper, the new technique which uses the state-dependent Riccati equation method for controlling the tandem cold rolling is tested by simulations. The results of these simulations are included in the evaluations which show successful control during the passage of the weld.