A device for improving coercivity of ring-shaped NdFeB magnets, including: a sealed chamber provided with a rotating mechanism, a supporting mechanism and a spraying mechanism, wherein the supporting mechanism, respectively rotating mechanism includes - a fixed support frame being installed in the sealed chamber; - a roller having a central axis along a straight line and being arranged at an upper position of the support frame; the roller being adapted to rotate around its central axis; - a retractable member installed on the outer surface of the roller and being adapted such that the ring-shaped NdFeB magnet can be sleeved on the retractable member, the retractable member being adapted to switch between a contraction state and a support state, wherein when the retractable member is propped up in the support state, the ring-shaped NdFeB magnet can rotate synchronously with the roller, and when the retractable member is contracted in the contraction state, the ring-shaped NdFeB magnet no longer rotates with the roller; a sliding rail provided at the lower part of the support frame and adapted to reciprocate up and down along the fixed support frame, the sliding rail being provided with a support groove, the support groove adapted to reciprocate along the sliding rail and located under the roller, the sliding rail being adapted to move the support groove up and down to a state where the support groove can hold or separate the ring-shaped NdFeB magnet; and the spraying mechanism includes - a first spray gun being provided at an axial end of the roller away from the support frame and being adapted to pass through the ring-shaped NdFeB magnet when supported on the support groove to spray the inner side of the ring-shaped NdFeB magnet; - a second spray gun and a hot air drying spray gun arranged on one side of the roller and adapted to spray the outer surface of the ring-shaped NdFeB magnet when rotated with the roller. a sealed chamber provided with a rotating mechanism, a supporting mechanism and a spraying mechanism, wherein the supporting mechanism, respectively rotating mechanism includes - a fixed support frame being installed in the sealed chamber; - a roller having a central axis along a straight line and being arranged at an upper position of the support frame; the roller being adapted to rotate around its central axis; - a retractable member installed on the outer surface of the roller and being adapted such that the ring-shaped NdFeB magnet can be sleeved on the retractable member, the retractable member being adapted to switch between a contraction state and a support state, wherein when the retractable member is propped up in the support state, the ring-shaped NdFeB magnet can rotate synchronously with the roller, and when the retractable member is contracted in the contraction state, the ring-shaped NdFeB magnet no longer rotates with the roller; - a fixed support frame being installed in the sealed chamber; - a roller having a central axis along a straight line and being arranged at an upper position of the support frame; the roller being adapted to rotate around its central axis; - a retractable member installed on the outer surface of the roller and being adapted such that the ring-shaped NdFeB magnet can be sleeved on the retractable member, the retractable member being adapted to switch between a contraction state and a support state, wherein when the retractable member is propped up in the support state, the ring-shaped NdFeB magnet can rotate synchronously with the roller, and when the retractable member is contracted in the contraction state, the ring-shaped NdFeB magnet no longer rotates with the roller; a sliding rail provided at the lower part of the support frame and adapted to reciprocate up and down along the fixed support frame, the sliding rail being provided with a support groove, the support groove adapted to reciprocate along the sliding rail and located under the roller, the sliding rail being adapted to move the support groove up and down to a state where the support groove can hold or separate the ring-shaped NdFeB magnet; and the spraying mechanism includes - a first spray gun being provided at an axial end of the roller away from the support frame and being adapted to pass through the ring-shaped NdFeB magnet when supported on the support groove to spray the inner side of the ring-shaped NdFeB magnet; - a second spray gun and a hot air drying spray gun arranged on one side of the roller and adapted to spray the outer surface of the ring-shaped NdFeB magnet when rotated with the roller. - a first spray gun being provided at an axial end of the roller away from the support frame and being adapted to pass through the ring-shaped NdFeB magnet when supported on the support groove to spray the inner side of the ring-shaped NdFeB magnet; - a second spray gun and a hot air drying spray gun arranged on one side of the roller and adapted to spray the outer surface of the ring-shaped NdFeB magnet when rotated with the roller.