Objective To ensure the thorough and efficient disinfection of the chlorination process amid fluctuating inlet water quality and flow this study proposed the introduction of active disturbance rejection control technology and an extended state observer to optimize the control of chlorine dosage. Methods Traditional feedback control strategies are ineffective in dealing with variations in influent water quality and flow rate. Therefore an active disturbance rejection controller was employed to address control issues in the chlorination system. The active disturbance rejection controller employed an extended state observer to promptly estimate total disturbances within the system including inaccuracies in internal models and external disturbances. It effectively addressed uncertainties and disturbances providing precise data support for control decisions. This enabled precise control of free residual chlorine thereby enhancing system robustness and response speed. Results Through simulation analysis it was found that the active disturbance rejection control strategy outperforms traditional control strategies in terms of metrics such as overshoot settling time and integral of the absolute error. It exhibited significant advantages in handling variations in water quality and external disturbances. Even in cases of model mismatch it demonstrated excellent control effectiveness making it particularly suitable for scenarios sensitive to environmental changes and requiring high control precision. Conclusion The integration of active disturbance rejection control and an extended state observer significantly enhances the adaptability of the chlorination process in water plants. This method can quickly respond to changes and timely track water quality requirements achieving precise control of free residual chlorine while improving the robustness and response speed of the system. It provides an effective solution for coping with variations in water quality and flow rates and is expected to be applied in the field of tap water production.