Abstract: During the transformer electrical tests, it needs to adjust the on-load tap-changer manually because of the power failure of substation, which is time-consuming and laborious. According to the electric screwdriver, an electric shift gear device of the transformer on-load tap-changer is designed based on actual situations, which changes the manual mode into electric adjustment and set the fixed number of revolutions. This device is used for electrical tests of substations in Chaoyang, and it is proved that the device can improve the working efficiency of the on-load tap-changer.