As a new control strategy, auto-disturbance- rejection control (ADRC) has been introduced in the power system successfully. The controller is free of planting model foundation in the design procedure and realized simply. In this paper, a ADRC controller used for superconducting magnetic energy storage (SMES) unit connected to a power system is proposed. Purpose of designing such controller is to improve the stability of the power system in a relatively wide operation range. The design procedure takes into account the active and reactive power cooperative control scheme. Simulation results show satisfactory performance and good robustness of the controller. The feasibility of the controller is testified as well.