The invention belongs to the technical field of pour point depressants and particularly relates to an aromatic ternary polymer diesel pour point depressant and a preparation method thereof. The pour point depressant is a tetradecyl methacrylate-long-chain alkyl maleimide-benzyl undecylenate ternary polymer which is prepared by the steps of polymerizing three monomers: tetradecyl methacrylate, maleic anhydride and benzyl undecylenate; and then performing an amination reaction with fatty amine. The synthetic method provided by the invention is simple and the raw materials are cheap and easily available; the aromatic ternary polymer diesel pour point depressant has the advantages of being stable in performance, effectively improving the condensation point and the cold filter plugging point of diesel, being small in additive dosage and good in pour point depression effect, etc.