© 2017 Technical Committee on Control Theory, CAA. An active disturbance rejection controller (ADRC) is designed and originally implemented on a real torsional plant. The torsional plant resembles the dynamics of a rotational system. Due to mass imbalance, centrifugal imbalance, and the non-coincidence between the principal and geometric axes of a rotating disc, the system parameters of this torsional plant are varying constantly. In addition, an input voltage disturbance could change the angular displacement of the rotating disk. In this paper, the ADRC is applied to drive the angular displacement of the rotating disc to a desired signal in the presences of system uncertainties and external disturbance. Both simulation and hardware implementation results demonstrate the effectiveness of the ADRC. Moreover, frequency response analyses prove the stability and robustness of the controller.