The invention relates to a CO boiler having the dustproof function and the denitration function. The CO boiler having the dustproof function and the denitration function comprises a flue, a combustion chamber, steam drums, an evaporation section and an economizer section. The CO boiler further comprises an ammonia spraying and mixing mechanism and a dustproof denitration reactor. The ammonia spraying and mixing mechanism is arranged above the evaporation section or between the evaporation section and the denitration reactor. The dustproof denitration reactor is arranged between the evaporation section and the economizer section and comprises a mixed-smoke inlet section, a denitration section and a purified-smoke discharging section, wherein an ash removal section is arranged between the mixed-smoke inlet section and the denitration section, ash baffles are arranged in the ash removal section, an ash bin is arranged in the denitration section, the center line of the ash bin and the center line of the reactor coincide, and the lower end of the ash bin is connected with an ash discharging pipeline. According to the CO boiler having the dustproof function and the denitration function, the denitration reactor is arranged in the CO boiler, so that the utilization rate of smoke heat is increased; due to the fact that the ash removal section is arranged in the reactor, smoke dust of mixed smoke can be removed before the mixed smoke enters denitration units, catalyst hole channels are prevented from being blocked, and the denitration efficiency and the denitration effect are improved.