A protection unit for a driving socket of a hub includes a hub with a driving socket connected to an end thereof and the driving socket has multiple ribs extending axially on the outer surface thereof. At least one protection unit is located between two ribs and has an engaging portion. A cover includes a cover face and two sidewalls so as to form an engaging groove. The engaging portion is engaged with the engaging groove. The three sides of the engaging portion are protected by the cover. The cover can be easily mounted to the ribs by the engagement of the engaging portion and the engaging groove so that the cover does not slip away from the ribs in radial direction.