The invention belongs to the technical field of building material metallurgy, and particularly relates to a preparation system for producing building material products through gradient utilization of pyrolytic steel slag. The preparation system for producing building material products through gradient utilization of pyrolytic steel slag comprises a raw material bin, a suspension type iron remover A, a conveying reamer, a steel slag vertical mill, a suspension type iron remover B, a built-in conveying reamer, an elevator A, a magnetic separator, a vibrating screen, a hot blast stove, a cyclone cylinder, a ball mill, a conveying chute, an elevator B, a micro powder bin, a circulating fan, a dust collector A, a dust collecting fan A, a chimney, a dust collector B and a dust collection fan B. According to raw material characteristics of the pyrolytic steel slag, the pyrolytic steel slag is subjected to graded utilization, easily-ground components are prepared into micro powder, difficultly ground components are prepared into coarse aggregate and fine aggregate, so that the production energy consumption is saved, the production cost is reduced, and the product types are diversified. The preparation system for producing the building material products by gradient utilization of the pyrolytic steel slag can meet the requirements of different customers.