The invention discloses a plant polysaccharide and a preparation method thereof as well as an application of the plant polysaccharide in cigarette. The preparation method comprises the following steps of: washing a plant and then drying, and extracting in water after smashing so as to obtain extract, wherein the weight ratio of the plant to the water is 1: (20-50); cooling the extract and then carrying out centrifugation and vacuum filtration, concentrating filtrate in vacuum until the volume of filtrate is 1/30-1/10 of that of the extract so as to obtain a concentrated solution; adding 95%-100% by volume of ethanol into the concentrated solution so that the volume fraction of ethanol in a system reaches 75%-90%; and stirring and standing for 8 hours-12 hours, centrifuging, collecting precipitate, carrying out freeze drying so as to obtain the plant polysaccharide. According to the invention, the plant is schisandra chinensis powder, Ludiju or fiveleaf gynostemma herb; and the method is simple to operate and low in cost, is easy to control and suitable for industrial production. The prepared plant polysaccharide is applied to the cigarette, the form of smoke is good when the cigarette is burnt and sucked, drying sense is reduced, mellow and full sense and aroma are increased, and brightness is obviously promoted.