The invention discloses a metal mixed lorry furnace shell down-warping correction and repair method which includes detaching various accessories of a metal mixed lorry furnace shell at first, maintaining cones on two sides of the furnace shell without any special treatments, arranging two electric hydraulic jacks between the bottom surface of a straight barrel of the furnace shell and a platform of a lorry body, circularly symmetrically cutting the upper portion of the straight barrel along joints of the cones and the straight barrel, cutting a small section of the lower portion of the straight barrel along a welding seam, keeping the furnace shell static, starting the two electric hydraulic jacks and jacking a down-warping portion of the bottom surface of the straight barrel of the furnace shell to the upper portion of the bottom surface of the straight barrel, leveling and positioning the joints of the straight barrel and the cones from the furnace outside to the furnace inside by hand hydraulic jacks then connecting the straight barrel with the cones in a butt jointing manner, manufacturing arc plates, rewelding the cutting portions, and finally mounting the various components of the furnace shell. By the method, down-warping of the furnace shell of the metal mixed lorry is corrected and repaired conveniently, scratch between the furnace shell and the platform of the lorry body is avoided, the service life of the furnace shell of the metal mixed lorry furnace is prolonged, and safety and normal running of the metal mixed lorry are guaranteed effectively.