Abstract: Non-bypass FGD systems require the start-up and shut-down process synchronous with the primary turbines, which imposes higher demands for its security and reliability. In this paper the researches are mainly conducted on the operational optimization measures and improvement schemes after the removal of FGD bypass. Moreover, the optimization scheme and retrofit principle are proposed for the flue gas system, absorption tower, absorbent slurry preparation system, gypsum dewatering system, accident evacuation system, electrical system and thermal control system. Finally, it is suggested that the FGD system should be included as part of the “primary turbine” set, and the operation reliability of the desulfurization equipment should be improved to ensure the safe operation of the generating units.