The invention discloses a tool and a method for strengthening friction extrusion of structural member connecting holes, and belongs to the technical field of machining. The friction extrusion strengthening tool comprises three parts of a friction extrusion head, a necking, and a base plate. When the tool is used to strengthen a structural member connecting hole, under the condition of maintaining 0.02-1 mm extruding magnitude of interference between the friction extrusion head and the connecting hole, the friction extrusion head is rotated and is inserted into the connecting hole in uniform speed. After stopping rotation for 2-5 s, the friction extrusion head is pulled out. The rotation speed of the friction extrusion head is 100-1000 rpm, the insertion speed is 0.1-2 mm/s, and pulling-out speed is 0.3-2 mm/s. In the above process, residual compressive stress is formed near the wall surface of the hole, and plastic flow occurs to the material near the wall surface of the hole, and the material has lattice distortion, and dislocation density is increased, so as to realize friction extrusion strengthening on the connecting hole. The tool and the method are mainly used in strengthening of important structural member connecting holes in aviation, aerospace, trains, and ships, and other industries.