The invention discloses a high-speed vacuum coating online cutting device which comprises a vacuum box. A horizontally-arranged supporting rod is fixedly connected to the inner side wall of the vacuumbox, a cutter handle is in sliding connection with the front wall of the supporting rod, a heat dissipation pipe is arranged inside the cutter handle, the two sides of the cutter handle are providedwith a cooling liquid adding inlet and a cooling liquid outlet which are both connected with the interior of the heat dissipation pipe, the bottom of the cutter handle is provided with a cutter, the front wall of the supporting rod is provided with a sliding groove, the side, close to the supporting rod, of the cutter handle is provided with a sliding block corresponding to the sliding groove, thesliding block is in nested connection with the inner side wall of the sliding groove, and the cooling liquid adding inlet and the cooling liquid outlet are provided with corresponding liquid stop valves. Since the heat dissipation pipe is arranged, and cooling liquid is added into the heat dissipation pipe, heat produced by the cutter in the cutting process can be rapidly reduced, cutting is moreaccurate, the service life of the cutter is prolonged, and the device is worthy of being popularized energetically.