The work aims to design a new type of bag-sealing mechanism and achieve the continuous feeding of plastic film in the process of hot pressing, so as to improve the bag-making efficiency. A bag-sealing mechanism was designed with cylindrical extruding cylinder technology. The 3D model of key mechanism was established with SolidWorks to analyze the kinematics of the key structure. Motor speed was controlled with electronic cam curve. The control strategies of traction, heat sealing and cutting of bag-sealing machine were put forward. By changing the speed of traction motor, the function of hot pressing of packaging bags of different lengths on the same equipment was realized, and the hardware design and software programming of speed control system were completed. The prototype was made and the pressing experiment was carried out. The prototype was stable at 0.5 s and longer hot pressing time. The heat sealing speed reached up to 120 pcs/min, which was substantially equal to the speed of the existing bag-making machine. The rotary bag-sealing machine can continuously feed film in hot pressing process, which verifies the rationality of the mechanism.