The invention discloses a diesel oil low-temperature flow improver prepared by compounding polyethylene vinyl acetate T1804 and a hexadecyl methacrylate-mixed alpha-olefin copolymer, wherein the hexadecyl methacrylate-mixed alpha-olefin is a copolymer obtained by carrying out solution polymerization with hexadecyl methacrylate and mixed alpha-olefin (containing dodecene, tetradecene and hexadecene) as raw materials, under an action of an initiator benzoyl peroxide and with toluene as a solvent. In the diesel oil low-temperature flow improver, the hexadecyl methacrylate-mixed alpha-olefin has a relatively good synergism with the polyethylene vinyl acetate T1804, a cold filter plugging point and a condensation point of high-wax-content diesel oil can be effectively reduced, the lubricity of the diesel oil can be effectively improved, the cost of a refinery plant is saved, and the diesel oil low-temperature flow improver can be applied to diesel oil refined from cycloalkyl and paraffin based crude oils.