The invention relates to a hand-held convertor transformer core grounding current tester which comprises a main body and a sensor, wherein the output end of the sensor is connected with a sampling circuit; the output end of the sampling circuit is connected with an amplification circuit; the output end of the amplification circuit is connected with an analog filter I; the output end of the analog filter I is connected with a digital filter; the output end of the digital filter is connected with a singlechip signal amplifier; the output end of the singlechip signal amplifier is connected with an analog filter I, the digital filter and a display; the output end of the analog filter II is connected with the singlechip signal amplifier; a battery is used for supplying power to the components. The tester is flexible and variable in testing range, high in sensitivity and accuracy, comfortable to hold by hand, small in size, light in weight and convenient to carry over.