Abstract: The unit has fast load response, stable control of main parameters during variable load, and can be continuously put into AGC operation for a long time, which are the requirements of DCS coordinated control system for supercritical coal-fired units. This article on how to optimize XXXX supercritical coal-fired units of power plant DCS and inside part of the subsystem of coordinated control system has carried on the detailed elaboration, optimization results not only meet the requirement of power grid on the properties of AGC unit, at the same time, the operating parameters of the unit are stable and not over the limit, effectively ensure the safe and economic operation of unit, the work in the paper can be used as a reference for practical operation.