The invention belongs to the technical field of rapid forming, and particularly relates to a method for achieving multilayer bead welding of metal foil strips through combination of extra auxiliary heating and ultrasonic welding. According to the method, preheating is conducted on metal foil or a base body material in rapid forming, the metal foil or the base body material is softened through preheating conducted by an external heating field, good gas protection is provided, and the welding thickness and width of a metal foil sheet are increased under the condition that the ultrasonic welding power is limited, so that multilayer one-time ultrasonic bead welding or multilayer multi-time ultrasonic bead welding of the metal foil is achieved and a three-dimensional solid block is formed in the solid-phase connection mode. Finally, a machining platform controlled by a numerical control program is applied, so that geometrical characteristic machining of a needed part is achieved. A metal piece obtained according to the method has the advantages of being low in cost, high in efficiency, compact in organization, free of casting-state structure, capable of achieving rapid forming of a functionally gradient material and the like.