Abstract: In order to simplify the production process of ship plate steel, and reduce molten steel refining time to control the production pace, process improvement test, which used steel slag washing desulfurization substitution to ladle furnace (LF) desulfurization, was carried on. The influence of the oxidation of slag, the end point carbon content and the flow rate of argon gas flow on desulfurization rate in the slag washing process were analyzed. The results show that the desulfurization rate is below 20% when the final slag FeO mass fraction is greater than 25%; When the mass fraction of the end point carbon is less than 0.06%, due to the strong oxidation of the steel and the desulfurization rate of the steel is less than 20%, the mass fraction in the end point carbon can be controlled more than 0.1%; Increasing the flow rate of argon can increase the desulfurization rate, but the effect is not obvious when the flow rate is over 0.5 m³/min. This result provides the basis for steel slag-washing desulfurization process replaced by LF furnace desulfurization process.