Method for preparing joint made of dissimilar material by firstly ultrasonically prefabricating and secondly welding transition belt

The invention discloses a method for preparing a joint made of a dissimilar material by firstly ultrasonically prefabricating and secondly welding a transition belt. The method comprises the main steps of stacking at least one layer of metal foil on the surface of a to-be-connected material through ultrasonic rolling welding to form a stacking layer; after the stacking layer is prepared, cutting off a foil disconnected part at the periphery of the stacking layer by a milling cutter of an ultrasonic rolling welding system, and milling the stacking layer to form the transition belt with a proper shape and a proper size; directly welding the transition belt with another to-be-connected metal by a fusion welding method, a braze welding method or a diffusion welding method so as to obtain the joint made of the dissimilar material with the macrostructure being formed by the to-be-connected material, the transition belt, a welding seam and another to-be-connected material. The technical scheme has the characteristic