Abstract: The structure of PID weight control system in MK 95 cigarette maker was introduced, and its control principle was analyzed, including weight signal detection, control process, speed control of trimmer motor, realization of digital PID control algorithm, selection of PID parameters.Meanwhile, the calibration and correction of system were also discussed.The benefits of the cigarette weight control system carried out by adopting the PLC controller's PID algorithm included simple hardware design, online parameters regulation, fast responding speed, and accurate and reliable control, it could replace the original analogue control system completely.