A raw mill’s production line is to grind the raw material mixed with limestone, clay and basalt of certain proportion; it decides the quality of the cement clinker. The production efficiency and quality can be promoted by precisely controlling the proportion of the three raw materials and feeding automatically. The system’s controller is S7-400, and the measurement is done by the rotor scale produced by SHENCK. The variable speed device (VSD) of the feeder was controlled by the flow through the PID controller to realize the precise proportion. Moreover, the proportion can be set and the feeding quantity, the producing process can be monitored by the position machine (Win CC), to achieve production automation.