Abstract: Assessment accuracy of corona resistance for enameled wires remains a key industry challenge. In the paper, influence of steel ball electrode service duration on corona resistance testing for enameled wires was examined. Results revealed that failure time of enameled wires increased with the extending of steel ball electrode service duration regardless of median value or mean value. When steel ball electrode was used less than three months in normal operation, dispersion of the obtained failure time data showed little change compared to the initial data acquired with a new electrode. And both data groups showed no statistically significant difference in mean values. However, when steel ball electrode had been used for over six months, failure time data exhibited a marked increase in dispersion, along with the emergence of extreme abnormally large values. Statistical analysis confirmed a significant difference in mean values between three-month and six-month datasets while showing no significant difference in median values. Therefore, to ensure the accuracy and stability of test results, users should regularly replace steel ball electrodes according to usage frequency and duration of corona resistance test equipment.