【Objective】The aims of this research are to explore the effects of sodium selenite on the antioxidant enzyme activities and fruit qualities of ‘Lvling’ walnut and to provide references for the effective application of selenium fertilizer in selenium rich walnut production.【Method】The 15-year-old ‘Lvling’ walnut trees were used as the materials, and different concentrations of sodium selenite solutions were sprayed onto the leaves. The fruits were collected during the fruit ripening season and the kernel antioxidant enzyme activities and the fruit qualities were determined. Principal component analysis was used to evaluate the fruit traits.【Result】The kernel SOD, POD and CAT activities were increased and the MDA content was decreased by spraying a suitable concentration of sodium selenite onto the leaves, and the antioxidant capacity was improved. The kernel SOD, POD and CAT activities were the highest after spraying 200, 80, 120 mg/L of sodium selenite solution respectively, which were 2.65, 9.30, 246.98 U/(g·min), which increased by 61.59%, 31.54%, 104.89%, respectively, compared with CK. The MDA content of the kernels was the lowest after spraying 120 mg/L sodium selenite, which was 2.27 μmol/g. After sodium selenite solutions had been sprayed onto the leaves, the nut yields increased, but there were no significant differences between the sodium selenite treatments. When the sodium selenite concentration was 160 mg/L, the nut weight was 13.42 g, which was the highest, which was 6.85% higher than the CK. The kernel soluble sugar, starch, soluble protein, total protein, and fat content increased after spraying sodium selenite had been sprayed onto the leaves, and their contents reached their maximum when the spraying concentrations were 120, 80, 120, 200, 120 mg/L, respectively, and the contents were 2.41%, 0.88%, 0.84%, 23.09% and 70.70%, respectively. The selenium content of the kernels increased significantly after sodium selenite was sprayed onto the leaves and the content was 0.10-0.16 mg/kg, which reached the selenium-enriched standard. There was found to be a highly significant positive correlation between the kernel selenium content and the SOD activity, yield, nut weight, nut longitudinal diameter and the soluble sugar content, and the correlation coefficients were 0.96, 0.89, 0.92, 0.91 and 0.77, respectively.【Conclusion】After spraying appropriate concentrations of sodium selenite onto the leaves, the nut yield increased, and the external qualities of the walnuts such as the nut weight, horizontal diameter, vertical diameter, and the side diameter as well as the internal qualities of the walnuts such as the selenium content, soluble sugar, soluble protein, total protein, and the fat content significantly increased, and the kernel antioxidant capacity improved. Evaluation using principal component analysis showed that the walnuts had the best characteristics when 120 mg/L sodium selenite was sprayed onto the leaves.