The oil-wetted air filter is a vertical drum container made of steel plate. The inner part of the barrel is divided into three parts: the outer interlayer, the inner interlayer and the straight pipe section. The upper part of the inner interlayer is provided with a swirl guide vane and a packing filter layer, and the lower part of the barrel is an oil chamber. The air enters the outer interlayer of the filter from the horizontal tangent line, rotates and impacts the oil surface downward, causing the oil surface to fluctuate and the oil foam is lifted by the air flow. The air gets the oil bath here, and the dust and impurities contained in the air are stuck into the oil.