Abstract: Through analyzing slag system, alkalinity and chemical compositions of the deposited metal, a submerged-arc welding agglomerated flux for pressure vessel of anti-H₂S corrosion with Al₂O₃ -CaF₂ -MgO-SiO₂ -MnO-TiO₂ fluoride and alkaline type slag system was developed.The experimental results indicate that agglomerated flux matched two kinds of welding wire made in institute of metal research chinese academy of sciences can both produce high tensile strength and low temperature impact toughness and good properties of the resistance to H₂S corrosion.For matching the 1^# welding wire, the weld metal have a relatively large component of Mn, brings down the γ→ αtransformation temperature, acicular ferrite increases in the weld metal.Thereby, the welded metal have higher low-temperature impact toughness.The low content of C, S and P has contributions to enhance the strength and impact toughness of the weld metal.The content of oxygen is only 0.035% and nitrogen is only 0.008%.The oxygen content reduces, which causes to produce bigger dimples in the ductile fracture appearance.At the same time the number of acicular ferrite increases, so the impact toughness is enhanced.