Abstract: The mechanical structure of and position relationship between cut-off knife and ledger in the improved YJ19 cigarette maker were analyzed,and the makeup and realization of the electrical system were discussed.Bosch AC servo motor was adopted to ensure the synchronization between knife disc and the independently driven ledger.In the range of ±0.05mm,knife and ledger would not interfered between each other,the synchronic tracking error of each motor kept in the range of 0.05°-0.1°.The system performs well in practice.