Abstract: A two-order model for phthalic anhydride production process with time delay has been proposed with synthetic method of mechanism analysis and system identification, and a self-tuner with a feedforward PID structure has been designed. A two-stage micro- computer control system structure is proposed as a simple distributed- computer control system. The software in the higher level computer, used for the controlling, monitoring and managing of the total system is designed. The operation of the system shows that the system is reliable and steady. It's control precision meets the requirements of the design.