Abstract: A clamping structure for a handled tool comprising: (1) a chuck body, provided with gear teeth, ratchet and guiding holes, (2) a plurality of grippers, mounted in the guiding holes of the chuck body and having partial thread on one end; (3) an inner gear ring, (4) a control outer sleeve, having a plurality of control keys and a plurality of driving keys thereon, (5) a driving member having inner taper thread and a plurality of pinions thereon, wherein the inner taper thread engages with the threads of the grippers, and the pinions, mounted to the driving member through pin shafts, engage with both the inner gear ring and the gear teeth of the chuck body, (6) a plurality of resilient anti-loose members with pawl. While the outer sleeve is rotated, its driving keys drive the inner gear ring rotating, which further causes the pinions, which engages with the inner gear, driving the driving member rotating around the chuck body.