Zr-0.75Sn-1Nb-0.35Fe-0.15Cr (wt.%) alloy plates were prepared by smelting, hot rolling, cold rolling and annealing techniques successively. The samples were then irradiated on an electrostatic accelerator with Ar+ to a fluence of 1.02×1015 and 5.1×1015 ions/cm2 (corresponding to 1 and 5 dpa, respectively) at 300 ℃. Both the unirradiated and irradiated samples were exposed to 360 ℃/18.6 MPa/0.01 M LiOH aqueous solution for 90 d. The microstructures of the alloy matrix before and after irradiation and the oxide film formed after corrosion were characterized by scanning electron microscope and transmission electron microscope. The results showed that before irradiation the alloy was fully recrystallized and the grains were equiaxed. The second phase particles were mainly Zr(Fe,Cr,Nb)2 with a fcc or hcp structure, and their size was within the range of 50~100 nm. After irradiation, -type dislocation loops were observed in the irradiated region of the alloy, and the second phase particles were completely amorphous, but the element diffusion from the second phase particles to the matrix was not found. After 90-d corrosion, the oxide film thickness of the irradiated samples was smaller than that of the unirradiated sample, indicating that Ar+ irradiation decreased the corrosion rate of the alloy to some extent at early stage of corrosion. This can be explained by the fact that Ar+ irradiation could delay the microstructural evolution of oxide film, including reducing the proportion of equiaxed grains and the number of cracks in the oxide film, as well as slowing down the oxidation of amorphous second phase particles induced by irradiation, thus enhancing the protectiveness of the oxide film.