The work aims to design a new type of automatic capping machine of the automatic filling production line, to achieve the automatic separation, grabbing, tumbling and moving and pushing down of the mass produced covers. With single cylinder as the only power, the capping machine was designed based on a special crank rocker mechanism, which turned the rectilinear movement of the cylinder into compound movement of the end actuator to achieve the capping process. The movement trajectory was verified through mechanism kinematic simulation in Pro/E. The end position equation of the crank rocker mechanism was derived. The motion simulation model of the mechanism was established. The position and velocity curve of the end effector as well as the spatial range occupied by the movement of the cover body were obtained through kinematics simulation. The feasibility of the design was verified and the development cycle of the products was shortened. The crank rocker mechanism is used to complete the integration of capping machine movement process, and the functions of automatic capping machine are achieved through a single power source. The capping machine, characterized by simple structure, easy operation, high working efficiency and good stability, can be easily integrated with all kinds of filling machinery.