The utility model discloses an automatic feeding and discharging mechanism, which is arranged on a stand of a machine tool, and comprises a feeding device, a grabbing device and a clamping device, wherein the feeding device is arranged on the stand and is provided with a conveying track for conveying a workpiece to a position to be processed; the grabbing device comprises a linear motor vertically arranged on the stand, a mounting rack connected onto a mover of the linear motor, a grabbing piece arranged at the lower part of the mounting rack and provided with a workpiece accommodating groove, a first air cylinder crosswise and horizontally arranged at the lower part of the mounting rack and used for ejecting out the workpiece in the workpiece accommodating grove of the grabbing piece, and a second air cylinder crosswise and horizontally arranged on the stand and used for ejecting the workpiece in the position to be processed into the accommodating groove of the grabbing piece; and the clamping device is arranged on the stand, and comprises a clamping piece provided with a branched clamping part, a clamping ring sleeved on the branched clamping part, a third air cylinder for driving the clamping piece to move crosswise and horizontally, and a fourth air cylinder arranged on the clamping piece and used for ejecting the workpiece in the branched clamping part out. The automatic feeding and discharging mechanism disclosed by the utility model has the advantages of simple structure, accurate action, low cost and the like.