The invention discloses an automatic feeding mechanism, which comprises a frame, wherein the frame is provided with a worktable; a screw mandrel is arranged below the worktable on the frame; one end of the screw mandrel is coupled with an output shaft of a servo motor on the frame; the screw mandrel is sleeved with a push pawl seat; the rotation of the screw mandrel can drive the push pawl seat to move to and fro; a push pawl is arranged on the push pawl seat; an iron pressing plate is arranged above the worktable; and a gap through which fed materials can pass is reserved between the iron pressing plate and the worktable. The automatic feeding mechanism greatly improves the safety factor and work efficiency of a punching machine and can be widely used as the feeding mechanism of various ordinary punching machines.