The utility model discloses a grinding plate component for a portable valve grinding machine. The grinding plate component comprises a grinding main rod and a grinding plate which are connected through a connector, wherein two permanent magnet mounting shaft holes are formed in the inner wall of the middle lower part of the grinding main rod, and two rotating shafts, between which a permanent magnet is mounted, are respectively mounted in the two permanent magnet mounting shaft holes, with one rotating shaft provided with a swinging arm; a soft magnet seam allowance seat is arranged below the two permanent magnet mounting shaft holes and is fitted with a soft magnet therein; the connector comprises a seam allowance pin; an opening penetrating up and down is formed in the center of the grinding plate. The grinding plate component further comprises a grinding pressure plate below the grinding plate, and a seam allowance matched with the seam allowance pin is formed in the center of the grinding pressure plate. The grinding plate component makes the best of characteristics of the permanent magnet and the soft magnet body to achieve very high efficiency in grinding paper installation and replacement, maintenance time saving and labor intensity reduction.