The invention discloses a stretch-forming and electromagnetic combining incremental forming method and device of a large thin-wall part. The method comprises the steps that a driving plate is arranged above a plate to be deformed, the driving plate and the plate to be deformed are clamped by a pressing plate and a supporting plate, and a lifting oil cylinder drives the supporting plate to move, so that the driving plate and the plate to be deformed are stretch-bent and tightened preliminarily, and the stretch-forming process is achieved; the position of an electromagnetic coil is adjusted, the electromagnetic coil is made to exactly face the driving plate to be deformed to discharge electricity, the coil rotates on the surface of the driving plate for a circle around the axis of a male die, and the plate to be deformed is attached to the male die at the same height; then, the oil cylinder descends again to stretch-bend the plate, the coil discharges electricity to deform the plate to be deformed again, the plate to be deformed is attached to the male die, and the alternate forming process of stretch-forming, discharging, re-stretch-forming and re-discharging of the plate is achieved in the same way till deformation of the plate is finished. The flowing evenness of materials can be improved, the thinning ratio of the plate can be reduced, and flexible processing and precise plastic manufacturing of large plates hard to deform can be achieved.