The invention relates to a technique for processing methanol-to-propylene by-products. The technique is characterized by comprising the steps as follows: a liquid hydrocarbon by-product of methanol-to-propylene (MTP) is separated to obtain a dry gas, a liquefied gas and C5<+> non-aromatic and aromatic hydrocarbons after passing through two sections of fixed bed reactors of olefin aromatization and alkane aromatization; the dry gas and aromatic hydrocarbon are discharged out of a reaction system as products; the C5<+> non-aromatic hydrocarbon is returned to the alkane aromatization reactor to continue to react; the liquefied gas and the liquefied gas of the MTP process by-product enter the alkane aromatization reactor; a heat source required for aromatization of the liquefied gas is provided by a mode of adding methanol; the liquefied gas is converted into a mixed hydrocarbon product of taking aromatic hydrocarbon as a main component under the action of a molecular sieve based catalyst; and the mixed hydrocarbon product enters the dethanizer to separate after being processed by an oil-water separator. By adopting the process, gasoline aromatization and liquefied gas aromatization are combined, and the MTP by-product is effectively converted into the hydrocarbons. By adopting the process, the actual gaining rate of the liquid hydrocarbon by-product of the MTP can be up to 65-120%, and the hydrocarbon yield of liquid aromatization can be up to 32-40%.