Based on the flue gas circulation system equipped with the 230 m² sintering machine of Delong Steel Co., Ltd, the differences in the volume fractions of O₂ and the mass concentrations of CO, SO₂ and NO_x in the flue gas of each bellow branch pipe before and after the application of flue gas circulation technology are analyzed, and the reasons for the change in the mass concentration of these 4 flue gas components and the possible impact on the output and quality of sinter are analyzed. The results show that after the flue gas cycle, the average volume fractions of O₂ in the flue gas of the bellow branch pipe decreases by 13.26% compared with conventional sintering, the average mass concentration of CO increases by 34.98% compared with conventional sintering, and the emission reduction effect of flue gas circulation on SO₂ and NO_x is obvious, reaching 33.5% and 20.7%, respectively. In the actual application process, through the coordinated control of the circulating flue gas components, temperature and other parameters, and the use of the mixed air device, the circulating flue gas, hot flue gas through circulating cooling taken from different bellows are effectively mixed to ensure that the oxygen content in the upper circulating hood of the sintering machine is stable at more than 18%, and the temperature reaches the (235 ± 25) ℃ range.