Abstract: A quick-release mechanism includes a screw shaft rotatably extending through a first member, a central hole of a gear and a second member, the first member having a slot defined therein so that a plate is movably received therein which has a notch portion defined in a front end thereof so as to engage with the screw shaft and a first protrusion extending upwardly from a rear end thereof. The screw shaft has a groove longitudinally defined in an outer periphery thereof and the gear has a second protrusion extending inwardly and radially-from a periphery defining the central hole so that the second protrusion is received in the groove. A bolt is threadedly inserted into the first member and contacts the rear end of the plate which has a spring mounted thereto so as to bias the plate toward the bolt. A pinion driven by a motor is engaged with the gear so as to drive the gear and the screw shaft. The screw shaft is allowed to be pulled directly when the plate is disengaged from the screw shaft.