Abstract: At present, the programmable logic controller is widely used in various industries, itimproves the level of industrial production automation management for it can effectively reduce the labor costs and improve the work efficiency. The automatic control and processing of seed watermelons series products is the inevitable development trend of the industry. In this paper, the design of PLC control system for seed watermelons series products line is introduced. Siemens S7 series controller and WinCC are selected to realize the automation control of production process. Parameter setting can be carried out through the upper computer so as to realize real-time monitoring and historical data inquiry on the system operation interface. After the control system is put into use, the factory continuous production of all by-products of seed watermelons is realized; the accuracy and stability of production process can be guaranteed, and the efficiency of processing and production has been improved.