Abstract: Based on the deep dephosphorization process of molten steel out of converter, the various dephosphorization agents for secondary dephosphorization were investigated by laboratory scale experiments.The initial phosphorus content in steel and the amount of dephosphorizing agent added into the tube furnace were firstly determined.And then, the compositions of the Ca O-based and Ba O-based dephosphorization agent were investigated, respectively.The results shows that the best ratio of Ca O-based dephosphorizing agent is w (Ca O) ∶w (Ca F₂) ∶w (Fe O) = (65-70) ∶ (15-20) ∶ (10-20) , the best ratio of Ba O-based dephosphorizing agent with Fe O is w (Ba O) ∶w (Ca O) ∶w (Ca F₂) ∶w (Fe O) = (10-20) ∶ (55-65) ∶15∶10 and the best ratio of Ba O-based dephosphorizing agent without Fe O is w (Ba O) ∶w (Ca O) ∶w (Ca F₂) = (30-40) ∶ (55-65) ∶ (15-20) .