Abstract: The requirement for the steel production is achieving more varieties and smaller lot of products with higher quality and low cost. In the circumstance, the process computer system has to be designed to achieve a more flexible system, which has high expandability and maintainability, and capability to increase the software productivity. Then Japanese steel companies have regularly introduced leading edge computer technologies to satisfy the requirements for automatic process control systems. In 1986 Chiba Works needed to have the total process control system for cold rolling restructured. In order to satisfy these requirements, a new system concept, Autonomous Decentralized System (ADS) was adopted for the restructure of the cold rolling process system. By using the ADS architecture, higher productivity than the conventional systems could be really achieved, and an excellent capability to metabolize the system, such as online ability to expand, reduce, reform and maintain, could be confirmed. The actual data obtained from the current process lines prove our achievement of goal.