Abstract: The local corrosion behavior of 825 alloy in simulated formation water of gas field at 132 ℃ with H₂S partial pressure of 4.8 MPa, CO₂ partial pressure of 1.6 MPa, and chloride ion mass concentration of 42 750 mg · L⁻¹ under elemental sulfur-containing condition (mass of elemental sulfur coated alloy in per liter formation water was 10 g)and under elemental sulfur-free condition was investigated by corrosion coupon tests. The results show that under the elemental sulfur-free condition, 825 alloy almost did not corrode, and the corrosion rate was only 0.007 7 mm · a⁻¹ during corrosion for 6 d. The corrosion rate reached 0.055 2 mm · a⁻¹ duing corrosion for 3 d under elemental sulfur-containing condition, showing the serious local corrosion of the alloy. With the increase of the corrosion time, the area of local corrosion pits on the alloy surface, the maximum depth of corrosion pits and the corrosion rate increased. The corrosion products of the alloy under the elemental sulfur-free condition were very few and were mainly composed of FeCO₃. Under the elemental sulfur-containing condition, the surface corrosion products increased in amount with the corrosion time and were mainly composed of FeCO₃ and FeS. The elemental sulfur underwent disproportionation reaction at high temperature, producing H⁺ and S²⁻, making 825 alloy corrosion product film rupture, therefore promoting the local corrosion.