Posco has made tremendous efforts to improve poor working environments and to increase productivity in coke plants. By reducing the labour cost and process cycle times, we improve economic efficiency. Also, a new coal preparation technique for the coke process improves energy efficiency and environmental impact. The results show that the automatic operation leads to increase the rate of operation and production cost. In this paper, the economic effect of coke plant automation is analysed on basis of manpower, productivity in coke plants, rate of the operation, energy consumption and environmental protection in Kwangyang works from 1990 to 2000.