In order to improve the treatment efficiency of CO in sintering flue gas and solve the problems of environmental pollution and resource waste caused by imperfect existing treatment methods, this study proposes a novel process that the traditional air is replaced with sintering flue gas as the cooling gas in a sintering shaft furnace. In this study, by means of CFD-DEM coupling method and based on Fluent and Rocky simulation software, the gas-solid countercurrent flow was simulated and by compiling user-defined functions, the gas-solid countercurrent heat transfer is simulated within the Fluent simulation software, to focus on analyzing the effects of sinter particle diameter, gas-to-material ratio, and initial temperature of sinter flue gas on sintering cooling efficiency and CO removal effectiveness. The results indicate that significant improvements in sintering cooling effectiveness and optimal CO removal effectiveness can be achieved when the sinter particle diameter is below 0.036 m, the initial temperature of hot sinter ranges between 902 and 930 K, the gas-to-material ratio is maintained at 831~1 088 m³/t, and the initial temperature of cold flue gas ranges from 332 to 362 K. The findings of this study can provide theoretical support and technical references for the optimized design and industrial application of synergistic CO treatment processes for sintering flue gas.