Abstract: In order to achieve the‘energy saving and consumption reducing’ for the thermal phosphoric acid process，CaO·SiO₂·Al₂O₃·MgO-P₂O₅ premelted slag was taken according to the actual composition of phosphate ore in Yichang，Hubei province to explore experimental melting reduction conditions.The experimental reduction results of premelted slag were also compared with the actual ore samples. It was shown that the premelted slag only had the good reduction effect with the temperature above 1 400 ℃ under the direct molten reduction conditions，and at the same time，much of molten glassy slag was produced.Through the adjustment of the contents of SiO₂，CaO，and Al₂O₃，the reduction performance could be improved while the composition of SiO₂，CaO，and Al₂O₃ was close to the melted slag phases，such as α-CaSiO₃，melilite，and anorthite， which had low melting points.The CaO·SiO₂·Al₂O₃·MgO-P₂O₅ premelted slag would have the best reduction effect，when temperature was 1 550 ℃，fixed w（P₂O₅）=13%，w（MgO）=5%，adjusted w（Al₂O₃）=7.9%，and binary acidity of SiO₂ and CaO was more than 0.75.Under the same reaction conditions and with the similar slag composition，the reduction performance of the artificial slag with pure Ca₃（PO₄）₂ as phosphorous source was much better than that with the natural mineral of fluorapatite.

Key words: molten, reduction, phosphorous rock