The invention discloses a high-entropy flux cored wire for aluminum-steel MIG welding. Powder is prepared from, by atomic percentage, 5%-15% of Fe, 10%-20% of Al, 20%-30% of Co, 18%-35% of Cr, 20%-35%of Ni and 5%-13% of Cu, and the total percentage is 100%. Industrial high-purity copper tape is adopted for an outer skin material. A preparation method comprises the steps that firstly, a mother alloy is melted; secondly, atomized power is prepared by applying a vacuum gas atomization powdering technology; and thirdly, the high-entropy flux cored wire is prepared by the adoption of flux cored wire forming unit equipment. The high-entropy flux cored welding wire is used for aluminum-steel MIG welding, a high-quality aluminum-steel welded joint is obtained, the chemical compositions of weld metal are within a principal element range of a high-entropy alloy, and the high entropy of a weld is achieved. The weld has excellent strength and toughness, brittle intermetallic compound phases are eliminated effectively, and the good synthesized mechanical properties are provided.