The utility model relates to a testing device for polarity of a bushing current transformer of a main transformer. The testing device is characterized by comprising a primary emitting device and a secondary emitting device, wherein the primary emitting device is formed by sequentially connecting a power supply module, a single chip microcomputer module, a voltage boosting module and a transmitting module; and the power supply module is connected with the voltage boosting module, the single chip microcomputer module is connected with the transmitting module, and the transmitting module is connected with a terminal of a primary winding of the bushing current transformer. The testing device can accurately test polarity of common current transformers, and is suitable for polarity tests of large-impedance bushing current transformers of main transformers, electric reactors and the like, reminds the testing personnel of the test results directly via indicating lamp signals and pulse sound signals, and solves the problems that polarity tests of large-impedance bushing current transformers of the existing main transformers, electric reactors and the like cannot be carried out.