Considering the gas mixing-and-pressurization process which is strongly coupled and disturbed in an iron and steel plant, a two-level-distributed system structure with process level and operation level was designed according to the requirements of the production process. By analyzing the system demands and functions of the software, the intelligent control algorithms were developed by utilizing function module reuse. The application programs were seamlessly linked with the distributed control system by using the OPC communication technology and the ATL packaging technology. The automatic control and real-time control of calorific value and pressure for the mixed gas were finally realized. Actual applications have shown that the results meet the requirements of process control, and the quality of gas is improved.