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, the contents of [C], [Si], [Mn] and [P] in hot metal at the end of dephosphorization decrease, and the corresponding removal ratios increase. The P2O5 content in slag increases, and the CaO and SiO2 contents in slag decrease. 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 with increasing the Fe2O3 addition amount from 5 g to 30 g. With increasing the Fe2O3 addition amount, the oxygen potential and activity at the interface between the slag and hot metal increase. 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. With increasing the Fe2O3 addition amount 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%.