The utility model discloses a stable steel seal knocking tool, which belongs to the technical field of steel seal knocking, and comprises a hammerhead, a grip, a combined structure and an adjusting structure, the combined structure is arranged on one side of the hammerhead far away from the grip, and the hammerhead is movably connected with the grip through the adjusting structure; the combined structure comprises a fixing cover, a clamping block, threaded rods and nuts, the fixing cover is arranged on the side, away from the grip, of the hammer head, the clamping block is arranged on the side, close to the hammer head, of the fixing cover, the threaded rods are arranged at the top and the bottom of the side, close to the fixing cover, of the hammer head, and the nuts are arranged on the outer surfaces of the threaded rods. The stable steel seal hand-knocking tool is simple and firm in overall structure, not prone to loosening, falling off and the like, convenient to assemble and disassemble, wide in visual field of workers, capable of improving working efficiency and good in using effect, the overall length can be freely and conveniently adjusted according to using requirements due to the arrangement of the adjusting structure, and the tool is convenient to use. Therefore, the device can be suitable for various different conditions, and the practicability is enhanced.