Based on the characteristics of large delay and strong coupling in spray drying, a monitoring system of spray drying tower for soybean flour based on fuzzy PID is designed. According to the technological requirements, a cascade fuzzy control scheme is adopted for spray drying tower. The main circuit adopts fuzzy PID control, and the secondary loop adopts PI control. The upper and lower computer monitoring adopts Kingview and SIEMENS S7-300 series PLC. The simulation results show that the cascade fuzzy PID control has the advantages of fast speed, small overshoot and strong robustness compared with the conventional PID control.