The invention belongs to the field of preparation of chemical intermediates, and particularly relates to a preparation method of 1-adamantyl methy ketone. The preparation method comprises the following steps of step 1, enabling adamantane and liquid bromine to react, so as to obtain 1-bromoadamantane; step 2, using concentrated sulfuric acid as a catalyst, adding the 1-bromoadamantane and n-hexane, and dripping formic acid, so as to obtain 1-adamantanecarboxylic acid; step 3, enabling the 1-adamantanecarboxylic acid and thionyl chloride to react, heating and refluxing, extracting by benzene, and directly applying the extracting liquid for the reaction in next step; step 4, dripping a mixed solution of benzene, diethyl malonate and anhydrous ethyl alcohol into a mixed solution of magnesiumpowder, iodine, anhydrous ethyl alcohol and benzene, dripping a benzene solution of 1-adamantanecarbonyl chloride, extracting by benzene, drying and distilling, so as to obtain 2- adamantanecarbonyl diethyl malonate; step 5, adding glacial acetic acid, water and concentrated sulfuric acid into the residue. The preparation method has the advantage that the yield rate is high.