The invention discloses a screwing device for a nut of a shock absorber piston rod. The screwing device comprises a support, a power device, a screwing device body and a piston rod fixing device. The support is used for fixing and supporting the power device, the screwing device body and the piston rod fixing device; the power device comprises a driving motor, a speed reducer and a control circuit and used for outputting torque which is power for screwing the nut; the screwing device body is arranged below the power device and comprises an active rotating piece and a passive rotating piece, a nut screwing block is arranged on the lower portion of the passive rotating piece, and a blind hole matched with the nut to be screwed is formed in the lower portion of the nut screwing block; the piston rod fixing device is arranged on the lower portion of the support and used for clamping the piston rod and enabling the piston rod to be located under the blind hole. The screwing device has the advantages that the piston rod screwing torque can be strictly controlled, so that the throttling performance of a reset valve is improved, and the service life of the reset valve is prolonged; operation is easy, and production efficiency is improved.