Abstract: The corrosion behavior for Zr-1.0Fe-1.0Nb specimens heat-treated at 580 ℃ for 5 h after β-quenching and cold rolling was investigated in 400 ℃/10.3 MPa superheated steam by autoclave tests. HRTEM and SEM equipped with EDS were employed to investigate the matrix microstructure and the oxidation behavior of the Zr(Nb, Fe)₂ second phase particles (SPPs). Results show that the major SPPs are o-Zr₃Fe and hcp-Zr(Nb, Fe)₂. During the oxidation, Zr(Nb, Fe)₂ SPPs are first oxidized into amorphous oxides and the amorphous oxides will be further oxidized into m-Nb₂O₅ and m-Fe₂O₃ phase nanocrystalline oxides, and finally the oxides are dissolved into the corrosive medium. The oxidation of Zr(Nb, Fe)₂ is accompanied by the diffusion and loss of Fe and Nb elements with the loss rate of Nb larger than that of Fe, which contributes to large amount of defects within the oxidation layer and promotes the oxidation layer transition from columnar to equiaxed grains, deteriorating the corrosion resistance of the alloy.