The utility model relates to the technical field of mutual inductor polarity testing. The current transformer polarity detection device is provided with a self-checking loop. The device comprises a power unit and control buttons. the loop control switch comprises a first movable contact, a second movable contact, a first static contact, a second static contact, a third static contact and a fourthstatic contact; the indication unit comprises a first light emitting diode and a second light emitting diode; the first static contact and the third static contact are electrically connected with thepositive electrode of the first light emitting diode; the negative electrode of the first light-emitting diode and the positive electrode of the second light-emitting diode are both electrically connected with a first wiring terminal on the secondary side of the current transformer, and the positive electrode of the first light-emitting diode and the negative electrode of the second light-emittingdiode are both electrically connected with a second wiring terminal on the secondary side of the current transformer. The transformer polarity detection device is reasonable and compact in structure,convenient to use, simple and convenient to operate, efficient in test and capable of detecting problems existing in a test loop in time, and self-inspection can be conducted on the detection devicebefore the transformer polarity is detected.