The paper aims to improve the packaging and the stacking efficiency of packaging bags for solid particles and reduce the labor intensity of enterprise workers. With the Siemens PLC S7-1200 as the core, combined with the digital input SM321, digital output SM322 modules, a set of production line was designed for automatic packaging and stacking of food, fertilizer and other materials. Through design of servo motor drive, sensor input module and touch screen man-machine interface, the automatic control of production line was realized. Upon completion of production line solid mixing device, packaging bag weighing device and stacking robot, the packaging experiment of fertilizer was carried out on this basis. The weighing error of packaging bags was recorded and the center error of stacking was analyzed. The grabbing error was less than 0.2 mm. The control system has high reliability and high precision of packing stacking, which can greatly improve the efficiency of packing and stacking, and has a great market application prospect.