The invention relates to heat power engineering, in particular preparation of solid fuel for combustion, and can be used at thermoelectric power plants in furnaces where solid fuel is burnt. According to the method of determination of parts of components of mix of coal ranks of dust system of boiler, part of each component of coal mix is determined separately, with following milling and supply of mix to the furnace of the boiler, and the parts of the components of coal mix are determined by the lower heat of combustion of fuel mix for working mass. Use of the invention makes it possible to provide efficiency of determination of the parts of coal rank mix components by the results of analysis for lower heat of combustion of coal dust for working masssampled just from the coal flow upstream of the mill, or coal dust downstream of the mill.
