This paper aims at upgrading ladle equipment to achieve efficient dephosphorization in ladle with adding specialized dephosphorization oxygen lance, combined with the semi-steel dephosphorization process in Chengde Iron and Steel Company, the characteristics of oxygen jet was simulated by commercial Fluent software to optimize the design of specialized dephosphorization oxygen lance. The industrial experiments showed that the new oxygen lance performed better slagging and stirring effects, and the new process had a well dephosphorization rate which could reach 51.8%. At the same time, the dephosphorization rate showed an upward tendency with the temperature of semi-steel rising in the range of experimenting temperature. And the ratio of decarburization quantity and dephosphorization quantity was 3. 17：1.