Abstract: Introduction Aiming at the lack of automatic control level in the design of desulfurization system for early large thermal power generating units, unable to meet the safety requirements and low control efficiency of the unit under the current environmental protection policy. Method Based on the actual situation of the desulfurization system in Zhuhai power plant and years of operating experience, the paper explored how to set SCS and MCS regulation modes of desulfurization system reasonably, so as to improve the automation level of the desulfurization system, improved the safety and reliability of the system, reduced work intensity of staff, purpose of improving system and personnel efficiency. Result The results show that through the field situation in-depth analysis, make the control logic of the actual situation on site, the automatic control level of desulfurization system can be greatly improved, improve the safety stability and operating efficiency of the unit. Conclusion For the early large-scale thermal power unit desulfurization automation work is effective, it can provide reference experience for similar projects.