The invention relates to a method for preparing BTX and co-producing tetramethylbenzene from C9<+> heavy aromatic hydrocarbons. The method comprises: carrying out catalytic
cracking conversion on C9<+> heavy aromatic hydrocarbons to obtain a first-stage
hydrocarbon mixing product using BTX and trimethylbenzene as main components, and separating respectively with an ethane removing
tower, a
butane removing
tower, a
hexane removing
tower, a BTX removing tower and a trimethylbenzene removing tower to obtain
dry gas, liquefied gas, C5-C6 non-aromatic hydrocarbons, BTX, trimethylbenzene and C10<+> heavy aromatic hydrocarbons, wherein the
dry gas, the liquefied gas, the C5-C6 non-aromatic hydrocarbons and the BTX are adopted as products; carrying out a reaction on the trimethylbenzene and a certain amount of
methanol to obtain a tetramethylbenzene-rich second-stage mixing product, and separating the products to obtain
dry gas,
wastewater and liquid-state hydrocarbons, wherein the liquid-state
hydrocarbon products return to the ethane removing tower so as to be separated; and carrying out
crystallization separation on the C10<+> heavy aromatic hydrocarbons to obtain tetramethylbenzene and a heavy component residue liquid, wherein the tetramethylbenzene and the part of the heavy component residue liquid are adopted as the product, and the remaining heavy component residue liquid return to a catalytic
cracking reactor. According to the present invention, with the method, the
moving bed non-
hydrogen cracking and the tetramethylbenzene preparation using trimethylbenzene
alkylation are compounded, such that the BTX is produced at a maximum while the high added value tetramethylbenzene can be co-produced.