Abstract: A desulphurization experiment was carried out by adding BaO and B₂O₃ to an CaO-based slag. The result shows that the addition of BaO can decrease the melting point and viscosity of the refining slag, improve effectively the dynamics condition of metal-slag reaction, and increase the desulphurization ability of the refining slag. When the BaO content is between 15% and 25%, the desulphurization rate is more than 90%. But the addition of B₂O₃ has little influence on the desulphurization rate, just can be added instead of CaF₂ as a flux.