Abstract: This paper proposes an extended state observer (ESO) based control strategy to effectively reject the coupling, disturbance and uncertainties in the boiler-turbine unit. The parameter tuning rule of ESO and its effect on estimation and noise suppression ability are analysed. A 300 MW coal-fired boiler-turbine unit model is simulated. The results of the set point tracking simulation as well as the perturbation simulation illustrate that with well-tuned ESO parameters, the proposed control strategy achieves satisfactory control results and strong disturbance rejection ability. With ESO, the disturbance and system uncertainties can be estimated as an extended state and then compensated by the control law. Besides, the ESO based controller has simple structure, thus brings a lot convenience in engineering applications.