The invention relates to a preparation method of a rubber swelling inhibitor for methanol gasoline. The method comprises the following steps: dissolving hydroxy benzaldehyde in a solvent in a reaction vessel at normal temperature, adding fatty amine and alkali into the reaction vessel while stirring, heating to 50-140 DEG C, and reacting for 2-8 hours; adding halohydrocarbon into the reaction vessel while stirring, continuing reacting at 50-140 DEG C for 2-8 hours, and cooling to room temperature; and filtering the mixture in the reaction vessel, adding alkyl phenol into the filtrate, and stirring uniformly to obtain the rubber swelling inhibitor for methanol gasoline. When 0.01-1% of the rubber swelling inhibitor for methanol gasoline is added into M15-M100 different designations of methanol gasoline, the rubber volume swelling can be reduced by 40-90%. The rubber swelling inhibitor can effectively inhibit the swelling action of the methanol gasoline on the common rubber, and has certain corrosion inhibition protection actions on the engine metal parts.