Abstract: The excitation system and speed control system of thermal power plants are the core control links to ensure the safe and stable operation of generator units and improve the dynamic quality of the power grid. However, the secondary circuit has problems such as insufficient parameter tuning basis, poor matching between control logic and the dynamic characteristics of the primary system, and poor coordination between excitation and speed control. Therefore, this paper designs a parameter optimization and control performance improvement technology based on adaptive self disturbance rejection for the secondary circuit. This article establishes a control oriented model for the excitation regulator and the secondary circuit of the electro-hydraulic governor, and considers unmodeled dynamics, parameter perturbations, and external disturbances as total disturbances. At the same time, an adaptive mechanism is introduced into traditional self disturbance rejection control, and fuzzy reasoning is used to adjust the observation bandwidth and control bandwidth online, ensuring the optimality of parameters under various operating conditions. The experimental results show that the technology proposed in this paper has achieved optimization of secondary circuit parameters and improvement of control performance, laying an important foundation for the safe and stable operation of the excitation system and speed regulation system in thermal power plants.