The invention discloses an automatic grinding mechanism for blades, which comprises a workbench, a sliding seat arranged on the workbench, a first manipulator, a second manipulator, a fixed block arranged on the workbench, a first driving member, Supporting mechanism, knife back grinding device, blade grinding device and cleaning device; the blade grinding device includes a second driving member arranged on the sliding seat, a first bracket arranged on the second driving member, a first bracket arranged on the The first fixed shaft on the first bracket, the grinding piece set on the first fixed shaft, the first torsion piece set on the first fixed shaft, the third drive set on the sliding seat member, the second bracket set on the third driving piece, the rotating roller set on the third support, a plurality of first limiting grooves set on the turning roller, and the first positioning grooves set on the first The clip on the limiting groove, the first elastic piece on the clip, the arc pieces and the wiping assembly on the grinding piece.