A combinational bolt which comprises a screw unit and a sleeve unit. The screw unit has a plurality of threads on a surface of a front terminal, the threads make the screw unit connect with a target object, another terminal of the screw unit forms a first concave portion. The sleeve unit, which is set inside the target object, also connects and surrounds the screw unit. A sink-proof portion is set on the surface of one terminal of the sleeve unit, the sink-proof portion makes the sleeve unit clamp onto the target object, and the outer surface of the sleeve unit has a plurality of strengthen circle units and a plurality of cut slots, and a second concave portion forms inside the sleeve unit, the first concave portion and the second concave portion clamp together.
