The invention relates to the technical field of ceramic glaze and particularly relates to a preparation method of furnace transmutation sorghum red-flower glaze. A ground coat is prepared from feldspar, quartz, Soochow soil, calcite, glass dust, dolomite, chromic oxide, cobaltous oxide, ferric oxide and vanadium pentoxide; overglaze is prepared from feldspar, quartz, zinc oxide, Soochow soil, boron frits, cadmium-selenium haematochrome, silicon carbide and copper oxide. The preparation method comprises the following steps: firstly applying the ground coat on a green body after biscuiting; then applying the overglaze; and firing by adopting oxidizing flames of a roller kiln. By adopting formulae of the ground coat which is matte black with metallic luster and the bright-red overglaze as well as a special firing process, particularly control of the temperature-raising rate, the ground coat which is matte black with metallic luster is low in initial melting point, the green body and the glaze are compactly combined, the glaze is level and smooth, and the product is smooth, flexible, vigorous and decent in surface.