The utility model discloses a bolt protection device, its characterized in that: including dustcoat no. 1 and dustcoat no. 2, dustcoat no. 1 seals the open columnar structure of the other end for one end, overcoat policy of "literature and art should serve both people and socialism" two ends opening's columnar structure, dustcoat no. 1 with dustcoat no. 2 cup joints, a dustcoat inner wall sets up the screw thread, a dustcoat outer wall sets up the spout, sliding connection couple in the spout, two lower extremes of dustcoat set up the flange, the flange inboard sets up the annular groove, set up the sealing washer in the annular groove. The utility model discloses a dustcoat no. 1 and dustcoat no. 2 that the setting was cup jointed, the inner wall of dustcoat no. 1 sets up the screw thread, and the outer wall of dustcoat no. 1 sets up the couple, makes the utility model discloses being fit for not, the equidimension bolt uses the labour saving and time saving of dismouting process in addition.