The invention discloses a friction stir plug soldering method, relating to a plug welding method, aiming to solve the problem of keyholes left after friction stir welding and friction stir spot welding. The method is as follows: 1) performing friction stir spot welding on a welded workpiece by using an integral soldering set, inserting the soldering set in the welded workpiece progressively during spot welding, continuing to rotate the soldering set for 1-3s after the soldering set stops inserting, lifting the integral soldering set, and forming a keyhole in the spot welding center; 2) placing solder in the keyhole; and 3) performing friction stir plug soldering on the keyhole by using the combined soldering set, inserting the soldering set in the keyhole progressively in plug soldering, continuing to rotate the soldering set for 3-5s after the soldering set stops to insert, melting the solder, extruding redundant liquid solder, retaining the cylinder part on a stirring pin in a clamping hole of the clamping body, plastifying the cone part of the stirring pin under the action of friction heat, and filling in the keyhole to realize the friction stir plug soldering on the keyhole. The invention is used for repair welding of the keyhole of the friction stir welding and friction stir spot welding seam.