Abstract: To address the problems of significant cigarette circumference fluctuations, frequent manual adjustments, and difficulty maintaining precision during the production process of the ZJ17 cigarette making machine, this paper designs and implements a closed-loop control system for cigarette circumference that integrates manual and automatic modes. Taking the Siemens S7-300 PLC as the control core, the TP900 touchscreen as the human-machine interaction interface, and combined with the Lenze servo drive system, the system constructs an automatic control platform integrating real-time monitoring, intelligent decision-making, and precise execution. Through Industrial Ethernet, the system collects real-time statistical data of cigarette circumference (maximum value, minimum value, average value, standard deviation) from the comprehensive cigarette testing bench, and dynamically switches control modes based on indicators such as standard deviation: In the automatic mode, an adaptive PID algorithm is adopted to generate adjustment instructions, and the PLC controls the servo motor to drive the cam mechanism, dynamically adjusting the position of the large pressure plate to form a quality closed loop; In the manual mode, operators can directly intervene in the adjustment amount through the touchscreen according to the sampling inspection results of the cigarette measuring plate. Industrial application tests show that the system can significantly reduce the standard deviation (SD value) of cigarette circumference by approximately 15% and increase the circumference qualification rate to nearly 100%, realizing high-precision and high-stability control of cigarette circumference, and greatly improving the automation level and product quality consistency of the ZJ17 unit.