Abstract: The distribution of phosphorus in slag and deposited metal(Lp) of manual metal arc welding has been researched by means of experimental and theoretical analysis. The results indicated that Lp increased with the increase of coating basicity of the electrode or FeO in slag. Although there was a limit to the dephosphorization of the deposited metal, it was satisfactory through suitable selection of the value of FeO in slag and coating basicity of the electrode.