Abstract: From the view of the mill main driving control system,instability model of the electromechanical system and control strategy were researched. In the premise of ensuring the steady and dynamic performance of the control system,the model of main drive of two inertial systems was simplified,the inside and outside disturbance of the system was observed by linear extended state observer. By linear feedback and dynamic error feedback method,the detection and control of electromechanical system failure were achieved. The closed loop controller design method based on simplified differential equation model was proposed,and validated by simulation and experiment. The results show that this study has a significant effect on solving the instability caused by load changes of rolling mill system.