Abstract: The PS-316 programmable logical controller in main controller of COMFLEX-1 cigarette reservoir and transfer system had not been available for several years, therefore, the control system of MAGOMAT80 tray unloader in this system was modified as follows by analyzing the unloader structure and process flow:introducing PLC, AC frequency conversion technology and valve-island technology on the hardware side; adopting structural modularized programming on the software side, and adding new functions, including operation in the presence or absence of tray, touch operation of man-machine dialogue in Chinese, and graphic display of running status and failure information. The modified control system was stable and reliable, ease of operation and maintenance, and ensured the normal running of the tray unloader.