The invention relates to a friction welding technology and particularly discloses a friction welding repair method for a hollow steel drill rod. The friction welding repair method comprises the steps that a joint spare part is prepared; a fracture face of a rod body of the drill rod to be repaired is machined into a concave-convex face; then a welding face of the joint spare part is machined into a concave-convex face corresponding to the rod body; the joint spare part is connected with the rod body in a repair manner through a friction welding process to form the repaired new drill rod; and in the welding process, a convex face of the joint spare part is welded to a convex face of the rod body in a fit manner, inner flash generated in the welding process exists in a concave face of the joint spare part and a concave face of the rod body, and finally the inner flash in the convex faces is treated. The repair method is convenient to implement, the durability of the repaired drill rod can be guaranteed, the waste of the drill rod is reduced, and the mining cost is lowered.