The automatic refining control system was developed in BOF at the No. 3 steel making shop of NKK Fukuyama Works. This system contains some improved functions and the expert system, in order to reflect well experienced operator’s know-how about BOF blowing into the refining control system. Linking of mathematical models and the expert system, the system designs the optimum blowing pattern and makes accurate adjustments to that pattern. That has been enabled us to establish the formation of three-men per one furnace. And the system has also achieved stable blowing.