The invention discloses a method and a device for purifying CO in flue gas and inhibiting white mist by coupling. Flue gas is introduced into a honeycomb ceramic support coated with a CO catalyst, low-concentration CO is catalytically oxidized into CO2 by sufficient O2 in the flue gas, the purpose of CO purification is achieved, the flue gas is heated to 110 DEG C or higher for emptying by heat released by the catalytic oxidation reaction, and the requirement of white mist inhibition for temperature is met; the device comprises a CO concentration sensor, a temperature sensor, a CO catalytic oxidation layer, an oxidation reaction tower, a flue gas desulfurization tank, a packing layer I, a packing layer II, a chimney and a solenoid valve. The method and the device have high heat utilization rate and remarkable energy conservation and emission reduction effects, can efficiently purify CO in sintering flue gas, can avoid white mist produced after wet flue gas wet desulphurization and hasgreat significance in relieving environmental issues such as haze and the like caused by the white mist at present, the process is simple, the investment is low, and the operation cost is low.