The invention discloses a method for preparing quaternary ammonium salt with adamantyl. The method for preparing the quaternary ammonium salt with the adamantyl comprises the following steps of (A) evenly stirring and mixing adamantane formic acid, anhydrous ethanol amine, aluminum oxide and methanesulfonic acid, and then carrying out reaction through heating to obtain adamantane formic acid ethylamine ester; (B) stirring the adamantane formic acid ethylamine ester and methanoic acid till all solid is dissolved, carrying out heating, slowly adding formalin dropwise when the temperature reaches 50 DEG C, and heating to 80 DEG C to carry out reaction continually after dropwise addition is completed to obtain N, N-dimethyl adamantane formic acid ethylamine ester; (C) evenly mixing the N, N-dimethyl adamantane formic acid ethylamine ester and absolute methanol, slowly adding haloalkane dropwise, and beginning heating to carry out reaction after dropwise addition is completed to obtain the quaternary ammonium salt with the adamantyl. The method simplifies the process route and is simple and convenient to implement, the yield of reaction is up to 95%, post processing operation is simple and convenient and easy to implement, and the method is suitable for industrialized production.