Self-locking drill chuck

A self-locking drill chuck, comprising a drill body, a nut, a clamping jaw, a self-locking structure, a first ring, and a rotating sleeve, wherein the self-locking structure comprises a ring tooth and a locking piece, the locking piece has a locking end engaged with the tooth, the locking piece is arranged at a part rotating with the nut, the ring tooth is arranged on the drill body or a part rotating with the drill body, a tooth face of the ring tooth is directed toward the front of the drill chuck, the rotating sleeve is connected with a part for driving the locking piece to allow the locking end of the locking piece to be inserted into a tooth of the ring tooth, wherein the locking piece is a cantilever disposed on a second ring nested outside of the drill body, the second ring rotates with the nut, the second ring has a cantilever base portion in front of the tooth face of the ring tooth, and the cantilever extends to the circumferential direction of the cantilever base portion, and wherein the nut is fixedly secured to a nut sleeve, the second ring is disposed in front of the nut sleeve by a keyway fit, and the nut sleeve is provided with a groove matching with the keyway, the length of groove is corresponding to the angle of rotating sleeve rotating relative to the nut when the drill chuck is from self-locking state to self-locking state, and the rotating sleeve is provided with a key engaged with the groove.