This invention relates to a method for preparing p-xylene and propylene from methanol and/or dimethyl ether. This method comprises coupling two reaction processes, an aromatization reaction of methanol and/or dimethyl ether and an alkylation reaction of ethylene with methanol and/or dimethyl ether. The method of this invention produces p-xylene and propylene with a high selectivity by returning an ethylene-enriched component in reaction byproducts from preparation of p-xylene from methanol and/or dimethyl ether to the reaction system for performing alkylation reaction with methanol and/or dimethyl ether in the presence of catalysts.