Abstract: The blue circle oxide films on fuel rods near the welded zone by electron beam (EB) welding were formed after corrosion tests. The microstructure, the thickness and the composition of this oxide films were examined and measured. Corrosion tests for samples with a blue circle or after ion injection were further carried out under normal or strict condition. All tests and inspections mentioned above show that the samples with the blue circle have a perfect corrosion performance during further tests. Based on the results, the mechanism of the formation of blue circle oxide films is suggested as well as the remedies, which have been verified during the volume manufacture.