The article presents a description of the structure of the algorithm, mathematical and software systems. The general characteristics of the algorithm for determining heat losses in the hearth of a blast furnace based on the use of the heat balance of the lower zone are presented. Heat losses in the process of melting into the environment occur through the tuyere belt, steam and shoulders, determined by the difference between the incoming and outgoing parts of the zonal heat balance for the lower stage of heat exchange. Determination of heat losses by the heat balance in the lower stage of heat exchange makes it possible to estimate their value according to the current information about the operation of the furnace in specific raw material and operating parameters. The information support of the system is presented, the software architecture is described, the characteristics of the software modules are given, and fragments of its work are illustrated. The information modeling system is distinguished by taking into account the basic physical and chemical laws of the processes of the control object, the principles of system analysis, the use of modern principles for the development and construction of mathematical models, algorithmic and software. Heat loss control is necessary to assess the condition of the blast furnace refractory lining, rational gas distribution, and also to adjust the coke consumption.