The oxide film formed on low alloy steel-nickel-base alloy (Alloy 52M) clad weld in simulated pressurized water reactor (PWR) primary water environments can be affected by the heterogeneities in structure and chemical composition as the result of cladding and machining process. The surface morphology and the cross-section of the oxide films were observed by scanning electron microscopy and (SEM) and transmission electron microscopy (TEM). After immersion in 325 ^oC hydrogenated PWR primary water for 146h, more oxide particles formed on the cladding alloy were found at the location close to the cladding fusion line than at the location far away from the fusion line. The microstructure and chemical composition in the weld at various distance from the weld fusion line is characterized by metallography, SEM-EDS and electron backscattering diffraction. Ni and Cr contents in the cladded Ni-base alloy increased with increasing the distance from the fusion line, while Fe content decreased with increasing the distance from the fusion line. A higher iron content in the cladding alloy corresponded to more oxide particles formed on the surface after the immersion in PWR primary water. After immersion in hydrogenated high-temperature water for 1860 h, the morphologies of the oxide film formed on the cladded Ni-base alloy at different locations became similar. The cross-sectional observation shows that the oxide film exhibits a double structure with the external layer enriched in iron and the internal layer enriched in chromium.