The invention relates to a current transformer polarity tester. The current transformer polarity tester is mainly composed of a chip, a voltage stabilizing diode, a diode, a capacitor, a self-locking switch, a light-emitting diode, a triode and the like. Through a normally closed node of the self-locking switch, the capacitor is charged; in detection, the self-locking switch is pressed, the capacitor begins to discharge through a primary coil of a current transformer, generate induced voltage through a secondary coil, and provide a pulse signal for a trigger in the chip through the voltage stabilizing diode, diode, resistor and triode; the trigger conducts the corresponding light-emitting diode after outputting, the color of the light-emitting diode is observed to judge the polarity of the transformer. The tester is applicable to the current direction inspection of all types of current transformers. The device is convenient to use, easy to operate and manpower-saving, reduces the labor intensity and improves the testing efficiency and the polarity judging accuracy.