This paper discusses how a control system was used to manage the temperature of flue gas in a utility boiler, resulting in significant coal savings. By implementing a sequential control device, the boiler's temperature was controlled effectively, with the cold end wall temperature staying within a very close range of the desired temperature. The goal was to keep the difference between the actual and desired temperatures to within ±1℃, which was successfully achieved in the No.6 boiler of Huangtai Power Plant.