The invention discloses a workpiece clamping mechanism applied to a multi-axis numerical control machine tool. The workpiece clamping mechanism comprises a big bevel gear wheel, a bottom plate, multiple small bevel gear wheels, a chuck body and four claw discs, wherein the big bevel gear wheel is connected with a third siding plate body, the bottom plate is mounted between the big bevel gear wheel and the third sliding plate body, the small bevel gear wheels matched with the big bevel gear wheel are mounted on the bottom plate, the chuck body is connected to the outer portion of the bottom plate and the big bevel gear wheel in a sleeving manner and fixed to the bottom plate, and the four claw discs are the same in size and are slidably connected with the chuck body. A connecting hole groove is formed in the third sliding plate body. An annular step which is concentric with the big bevel gear wheel and is matched with the connecting hole groove is arranged on the big bevel gear wheel. A planar spiral groove is formed in the back of the big bevel gear wheel. Four radial sliding grooves distributed in the radial direction of the chuck body are formed in the chuck body. A chuck guide block matched with the corresponding radial sliding groove is arranged on the back of each claw disc. A spiral protrusion matched with the planar spiral groove is arranged on each chuck guide block. A through hole matched with a rotating hole is formed in the wall portion of the chuck body.