The invention provides a preparation method of sesquiterpene resin in which the turpentine of sesquiterpene with content being 86% is taken as a raw material to prepare the sesquiterpene resin. Anhydrous AlCl3 serves as a main catalyst, and HClO4 or/and CCl3COOH serve as an assistant catalyst; in the presence of solvent 1,2-dichloroethane or toluene, mixture reacts at the temperature of from -20 to 30 DEG C in the nitrogen atmosphere for 4-8 hours; polymerisate is distilled after acid pickling, alkali cleaning and washing; relative pressure is controlled to -1.5kPa, and discharging is carriedout at the temperature of 220-300 DEG C to obtain the sesquiterpene resin with different softening points; the yield of the sesquiterpene resin of which the softening point is more than 70 degrees can be 86%, and the sesquiterpene resin with high softening point being more than 110 degrees is 55%.