Abstract: The corrosion-resistance of the steel FV520B had been tested respectively in the HCl and H₂SO₄(10%) under the 35℃.The result showed that under the above condition the base metal and the welding welding joint suffered a much more serious pitting corrosion in the HCl(10%) than that in the H₂SO₄ of the same mass fraction, the chloridion has more serious destructive effect on the passivation film of the stainless steel, which causes the deeper corrosive pitting.while the corrosive effect of 10% mass fraction H₂SO₄ is relatively inferior, the corrosion products are different either, but under the different corrosive environment, all the corrosive level of the weld joint in the welding point is lower than the HAZ.