The utility model discloses a transformer braking unit maintenance test device. The device consists of an adjustable autotransformer, a booster transformer, a switch, a rectifying circuit, a filter capacitor, a direct current voltmeter, a true virtual value voltmeter and a bulb. The device is characterized in that the input of the adjustable autotransformer is connected with a 220V alternating current power supply; the output end of the adjustable autotransformer is connected with the input end of the booster transformer; the secondary tap of the booster transformer is connected with the input end of the rectifying circuit through the switch; the output end of the rectifying circuit is connected in parallel with the filter capacitor and the direct current voltmeter; the secondary output voltage of the booster transformer is rectified, filtered and then input to a braking unit to be tested; and the output of the braking unit to be tested is connected in parallel with the true virtual value voltmeter and the bulb. The device can be used for accurately measuring the turn-on and turn-off voltage thresholds of the converter braking unit and debugging the braking unit, is convenient to use, and can be widely applied to the use and maintenance occasions of motor converters.