The invention provides a current transformer and a switch cabinet using the current transformer. The switch cabinet comprises a cabinet body, wherein the cabinet body is provided with a charged display device; a current transformer is arranged in the cabinet body; the current transformer comprises a primary winding; the primary winding is connected with a signal power supply circuit; and the signal power supply circuit is provided with a voltage reducer in series. By using the voltage reducer, the signal power supply circuit can output a lower stable drive voltage signal to the charged display device, so that the charged display device can work normally. Since the signal power supply circuit is connected to the primary winding, the problem that the drive voltage signal is influenced by the size of the secondary winding is solved in the prior art, thereby ensuring the uniform brightness of the display lamps of the charged display device, facilitating the operating personnel to effectively judging the switch cabinet charging condition in time, and lowering the probability of the safety accidents of the switch cabinet.