This study has been carried out to investigate for the dephosphorization equilibrium between Cao-SiO₂-CaF₂, CaO-Na₂O-SiO₂-CaF₂ stags and molten steel containing chromium in the temperature range of 1550℃∼1600℃. The results obtained from the experiment are as follows. The solubility of Cr₂O₃ is shown to be increased by increasing MgO content due to the MgO·Cr₂O₃ formation regardless of basicity in the slags. The solubility of oxygen in the CaO-SiO₂-CaF₂ slags system is decreased in low [Cr] region, increased with increasing [Cr] content. The solubility of oxygen in the CaO-Na₂O-SiO₂-CaF₂ slags system is about 250 to 450ppm in low [Cr] region and 250 to 400ppm in high [Cr] region. The observed values of L_o are in fairly well agreement with the theoretical values calculated.