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In this paper, the influence of the Fe₂O₃ addition amount on the dephosphorization of hot metal at 1623 K with the slag of the low basicity (CaO/SiO₂) of about 1.5 was investigated by using high-temperature laboratorial experiments. With increasing the Fe₂O₃ addition amount from 5 to 30 g, the contents of [C], [Si], [Mn] and [P] in the hot metal at the end of dephosphorization are decreased and the corresponding removal ratios increase. In dephosphorization slags, the phosphorus mainly exists in the form of the nCa₂SiO₄–Ca₃(PO₄)₂ solid solution in the phosphorus-rich phase and the value of coefficient n decreases from 20 to 1. Furthermore, the oxygen potential and activity at the interface between the slag and hot metal are increased. When the oxygen potential and the oxygen activity at the interface are greater than 0.72 × 10⁻¹² and 7.1 × 10⁻³, respectively, the dephosphorization ratio begins to increase rapidly. When the Fe₂O₃ addition amount is increased to 30 g, the ratio of the Fe₂O₃ addition amount to theoretical calculation consumption is around 175%, and the dephosphorization ratio reaches the highest value of 83.3%.