Abstract: In order to suppress electromechanical vibration, to dynamically restrain the disturbance ot a main drive system and not to induce static error by the disturbance, a state space model of two-degree-of-freedom systems was built based on model matching techniques for the main drive system of a roiling mill. The design of an electromechanical vibration controller was converted into a standard H_∞ control problem. Then an output feedback H_∞ controller was obtained by using LMI approach so as to guarantee the robustness of the main drive system of a roiling mill. Simulated results showed that the controller effectively improved the performance of command following, suppressed electromechanical vibration, and reduced the dynamic speed fall caused by load disturbance.