The work aims to design a control system of the rectifying device combining torque observer and integral sliding mode variable structure algorithm to improve the control precision of the rectifying mechanism of packaging production line, and improve the appearance and qualified rate of product. On the basis of analyzing the structure of rectifying devices and taking rectifying servo motor as the research object, a motor control method was put forward. The load torque observer and the integral sliding mode controller could not only solve the effect of load disturbance on the performance of the control system, but also reduce the chattering amplitude of the sliding mode controller. In addition, the saturation function could further reduce the system chattering. The feasibility and effectiveness of the proposed method were verified by experiments. The experimental results showed that the control method basically had no overshoot, and it took about 0.5 s to reach the stable state. By adopting the rectifying device, the maximum deviation amount of the packaging film was only 0.70 mm, and the qualified rate of the packaging was above 97%. On the premise of ensuring product quality, the robust control system of rectifying devices can improve the qualified rate of products and the working efficiency of packaging production lines.