Abstract: In order to solve the problems of low production efficiency, low assembly quality and high labor intensity caused by manual adjustment and placement of hydraulic cylinder in the production process of hydraulic hinge, a kind of hydraulic cylinder assembly mechanism is designed. The mechanism is composed of feeding mechanism, detection and adjustment mechanism and clamping mechanism, which realizes automatic feeding of hydraulic cylinder, automatic detection and adjustment of pin hole orientation and automatic placement on the transmission fixture. It has been applied to the production line of hydraulic buffer hinge, and its method obtains a certain reference value for solving similar problems.