The utility model discloses a millstone-type automatic aligning sealer for a rod-pumped well opening. The sealer comprises a millstone-type automatic aligning device, a primary sealer, a primary sealer pressure cap, a secondary sealer, a sealer packing, a secondary sealer pressure cap and a connection clip, wherein, the millstone-type automatic aligning device is sleeved at the lower part of a sleeve; the sleeve below the millstone-type automatic aligning device is sleeved and connected with the threads or the lathedog of a wellhead; the sleeve above the millstone-type automatic aligning device is sleeved and connected with the primary sealer; the primary sealer is fastened by the primary sealer pressure cap; the secondary sealer is arranged outside the primary sealer pressure cap through threads; the sealer packing is arranged between the secondary sealer and the outer wall of the sleeve; the secondary sealer pressure cap is arranged outside the secondary sealer through threads and compresses the sealer packing; and the connection clip is sleeved at the upper part of the sleeve. By adopting the primary and the secondary sealers, the utility model has the advantages that the phenomenon of raw oil escaping is completely eliminated; the pumping rod is free from corrosion and can be used repeatedly; and the eccentric wear problem of the pumping rod is solved, so that the system efficiency of the oil pumping unit is improved, and the energy consumption is reduced.