Abstract: In view of problems of non-compatible communication protocol between new and old equipments and strong dispersion of field devices in reform process of monitoring and control system of high slag granulation of an Ironmaking Plant, a monitoring and control system of high slag granulation based on various communication protocols was designed. The system uses data integration mode with multi-level network and multiprotocol: field devices with ModBus communication interface use Profibus-ModBus protocol bus-bridge to finish data conversion from ModBus RTU to Profibus, field devices with Profibus-DP communication interface access DP network directly through respective Prifibus-DP communication board, field devices with AS-i communication interface integrate data in LOGO into master station of Profibus-DP through communication processor, unintelligent communication devices exchange data through several remote I/O slave stations composed of ET200M and I/O extended module; building independent process monitoring PC station in workshop of high slag granulation to real-timely monitor important parameters; integrating relative data of process monitoring PC station into monitoring center PC of enterprise management layer through protocol conversion. The actual application shows that the system has stable and reliable running and reaches reform requirements.