Abstract: For large inertia，lag and nonlinear characteristics in process of mill running，an expert system based on fuzzy self-optimizing control was put forward. Fuzzy control，self-optimizing control and traditional PID control are organically combined together，and used in control design of grinding classification system of a concentrator in Chengde. By combination of PLC and industrial control computer form a DCS system. Practice shows that the expert system for the safe and stable operation，energy saving effect is obvious. It can greatly reduce the labor intensity of on-site operation，and also improve their working conditions.

Key words: Expert system, Self-optimizing control, Fuzzy control, Mill load, DCS system