A wire grip is adapted for fastening a wire and mounted to a tension device which pulls the wire grip to produce a pulling force to the wire. The wire grip includes a basic body and a capstan. The capstan is slidably mounted to the basic body for fastening an end portion of the wire and enabling the wire to be wrapped thereon. The capstan is movable in a direction relative to an axis thereof whereby to ensure the pulling force provided by the tension device is in alignment direction with the pulling force received by a middle portion of the wire.