Abstract: The characteristics of oxide films formed on low alloy steel/stainless steel weld in oxygen-containing and deaerated simulated pressurized primary water at 290℃ were investigated. The results showed that the main corrosion product formed on the surface of A508Ⅲ low alloy steel in oxygen-containing high temperature water was γ-Fe₂O₃, while the surface film was mainly composed of Fe₃O₄ in deaerated high temperature water. The spinel oxide particles on 309L/308L cladding surface in deaerated high temperature water were larger and more extensive than those in oxygen-containing water. Reducing the oxygen content in high temperature water favored the formation of spinel oxide particles that were more extensive and larger on 309L surface than those on 308L surface. In oxygen-containing or deaerated water, pitting appeared on the surface of 309L, while the surface of 308L had no significant pitting. The preferential dissolution of inclusions of 309L in high temperature water was thought to be the main cause of pitting.