The invention relates to a preparation method of an additive for fungus polysaccharide cigarettes and an application of the additive in the cigarettes. The preparation method is characterized in that fungus polysaccharides are prepared by taking fungus as a raw material through the following method: getting the dry fungus, removing impurities, crushing, soaking, freezing, unfreezing, deproteinizing, boiling in water, centrifugalizing, concentrating, performing ethanol precipitation, filtering and drying. The additive for the fungus polysaccharide cigarettes is added into cut tobacco of the cigarettes, so that the moisture retention performance of the cut tobacco can be increased, the miscellaneous gas and the stimulus in smoke gas can be reduced, the aftertaste is sweet, fluid can be produced in the oral cavity, and the comfort of sensory organs is obviously improved. The largest characteristic of the preparation method disclosed by the invention is that a technology of combining temperature-difference wall-breaking with enzyme process deproteinization is adopted, a simple, effective and easy-to-amplify fungus polysaccharide extraction process is established, the fungus polysaccharides are applied to the cigarettes, the original performances of the cigarettes are not changed, the original processing process of the cigarettes is not changed, the processing performances and the comfort of the sensory organs of the cigarettes are improved, and the preparation method further has actual production significance and value.