Abstract: To control multivariable objects with high-order large inertia in a thermal system using a low-order controller, we propose a decentralized compensated active disturbance rejection control method by combining high-order compensation control and decentralized active disturbance rejection control. Consequently, we theoretically derive the closed-loop transfer function of the system. Using the inverse Nyquist array design method in the multivariable system, we quantitatively analyze the stability region size of the proposed decentralized compensated active disturbance rejection control and the conventional decentralized control method. The simulation results show that the decentralized compensated active disturbance rejection control is superior to the conventional decentralized active disturbance rejection control without compensation in terms of stability region size, dynamic performance, and robustness. It improves the control performance of a high-order multivariable system controlled by a low-order controller and has good application prospects.