The invention relates to the fields of machining equipment and electric tools, and particularly relates to a gear self-tightening drill chuck and a flat claw self-tightening drill chuck. The gear self-tightening drill chuck comprises an afterbody, a forebody, a front sleeve, a clamping jaw, a driven bevel gear and a retaining device, wherein the afterbody is arranged in the forebody; a driving bevel gear is arranged on one end of the afterbody; the driving bevel gear is engaged with the driven bevel gear; internal threads are formed on the driven bevel gear; external threads are formed on the clamping jaw; a back hole is formed in the forebody; the afterbody, the driving bevel gear, the forebody and the front sleeve are coaxial; the retaining device comprises a front connector and a back connector; first helical teeth are formed in one side of the front connector; second helical teeth are formed in one side of the back connector; the front connector is arranged on one side of an end cover; the first helical teeth are formed in one side, which is far from the end cover, of the front connector; and the back connector is engaged with the front connector. According to the gear self-tightening drill chuck, the clamping of a drilling tool is not influenced when the drill chuck rotates clockwise, a drill cannot be loosened when the drill chuck rotates anticlockwise, and normal operation of the self-tightening drill chuck is guaranteed.