The combustion property of coke and washed powder are analyzed by a thermogravimetric analysis test, and then the influence of fuel combustion behavior on CO emissions in sintering exhaust gas under different fuel structures and particle size distributions is explored through a sintering cup test, and the formation mechanism of solid carbon in the pyrolysis and combustion process of solid fuels is deeply analyzed from the analysis of sintered CO generation mechanism, and the different effects on the change of internal temperature and oxygen potential of the material layer on the CO produced by fuel combustion caused by the change of sintering fuel structure and particle size distribution are described. The results show that, with the gradual increase of the proportion of washed powder, the CO volume fraction in the exhaust gas is increased gradually, especially after the proportion of washed powder exceeds 50%, the CO volume fraction is increased significantly from 2.12% to 2.60%, and the CO volume fraction in the exhaust gas is decreased significantly after the improvement of fuel particle size distribution, with a decrease of about 39.5%. Therefore, an appropriate increase in the proportion of washed powder in the sintering fuel and the increase of fuel particle size can effectively reduce the CO emission in the sintering exhaust gas.