Counting mechanism for hydraulic tightening device

A counting mechanism of a hydraulic tightening device comprising an oil input/output mechanism and a counting mechanism, wherein the counting mechanism includes a counter, a piston sealing, a driving piston, a spring, a spring cover, a counting unit, a piston restricting unit, a main body seal, a lower cover, a bolt and a restricting unit, wherein the piston sealing is disposed in a sealing trough of the driving piston and the driving piston is plugged into the counter and the spring covered by the spring cover is used to connect with the driving piston, and the spring cover is connected with the counting mechanism through the bolt, wherein the piston restricting unit is plugged into the a piston restricting trough to prevent the driving piston from rotating, wherein the lower cover is used to plug into the counting mechanism to secure the counter and the counting mechanism is secured on the hydraulic tightening device through the bolt, and the main body seal is used to seal a hydraulic oil path to prevent leaking, wherein the oil input/output mechanism is connected to the hydraulic tightening device through the counting mechanism, and once the hydraulic oil passes through the oil input/output mechanism, the counting mechanism automatically records as the hydraulic tightening device performs one more time.