The invention relates to a preparation method of 3-methyl-3-amylene-2-ketone. The preparation method comprises the steps of mixing butanone and a solid acid catalyst at 0-80 DEG C, adding acetaldehyde, fully mixing, reacting continuously, separating and purifying after reaction to obtain the 3-methyl-3-amylene-2-ketone, wherein the solid acid catalyst is highly-acidic dry type sulfonic acid group based polystyrene with H<+> or sulfonic acid group based perfluorination cation exchange resin. According to the method, the solid acid catalyst is adopted, compared with the traditional synthetic method that strong acid and strong base are used, the method can greatly reduce the follow-up separation difficulty and environment pollution degree, no equipment corrosion is caused, and the product yield and the purity are high, therefore, the preparation method of 3-methyl-3-amylene-2-ketone is green and environment-friendly; and besides, no assisted solvent is adopted, the follow-up separation difficulty is reduced, the energy consumption and the production cost are low, and the industrial reliability is strong.