Abstract: An online control software was developed by Visual C++6.0, WinCC 6.2 of Siemens, SQL Server 2005, etc., for the new heat-treatment system of alloy plate/strip hot-rolling line in Baosteel. Mainly the software comprises a man-machine interface, process computation model, communication softwares and real-time data management system. The modeling principle is described in detail. The online running results of the software developed showed that combining the plate-reheating system with basic automation is able to not only reduce the operation complexity but also greatly increase the precision of temperature control and quality of plates in the heating process.