The invention relates to a leakage current detector for a ground wire of a high-voltage cable shielding net. The leakage current detector comprises an aluminium alloy shell, wherein an alternating-current and direct-current power supply device and a detection device are arranged in the aluminium alloy shell; the anode and the cathode of the alternating-current and direct-current power supply device are respectively connected with a frequency selecting circuit; a secondary side of a current sensor is connected with an I/V conversion circuit through a shielding wire; the I/V conversion circuit is respectively connected with a bidirectional analog output port and the frequency selecting circuit; the frequency selecting circuit is respectively connected with a filtering circuit and a rectifying loop; the filtering circuit is connected with the rectifying loop; the rectifying loop is connected with a peak response time selecting circuit; the peak response time selecting circuit is respectively connected with the input ends of a peak holding loop and an LCD (Liquid Crystal Display) driving loop; and the output end of the peak holding loop 318 is sequentially and electrically connected with a voltage dividing loop, the LCD driving loop and an LCD display screen. According to the leakage current detector, the problem of cable burning loss caused by untimely discovery of multipoint grinding of a grinding wire of an existing cable shielding net is solved.