The invention discloses a fixed-length cutting-off device for sealwort. The fixed-length cutting-off device comprises a rack, a support seat, guiders, a blocking mechanism, a support, a servo motor, afirst gear, a feeding nut, a second gear, a lead screw, a guiding plate, limiting rods, a sucking mechanism, a tray, an air bellow, a cover plate, a draught fan, a photoelectric sensor, a stand column, a base plate, a speed adjustment motor, a rotating shaft, a cam, guiding wheels, a connecting plate, first guiding rods, a guiding block, a C-shaped bracket, a cutting-off mechanism and first springs. The fixed-length cutting-off device is simple in structure; fixed-length cutting-off can be automatically conducted on the sealwort; in addition, the cutting-off length can be adjusted; safety achieved in the sealwort cutting process is effectively improved; meanwhile, chippings can be removed automatically; the production process is simplified; and production efficiency is improved.