The invention discloses a high gradient magnetic separator, which comprises a separation ring and a driving device thereof, an ore feeding device, a concentrated ore discharging device and a concentrated ore collecting device, wherein the separation ring comprises a rotating ring and a concentrated magnetic medium pack, a left magnetic yoke, a left magnet, a right magnetic yoke, a right magnet, afront magnetic yoke, a rear magnetic yoke, and a magnetizing and demagnetizing device which consists of magnetic coils and a magnetizing power source and can perform magnetizing and demagnetizing treatment on the left magnet and the right magnet respectively. The high gradient magnetic separator smartly combines a permanent magnet and a magnetizing power source to form a background magnetic fieldof the separator, so the high gradient magnetic separator can conveniently perform magnetizing and demagnetizing treatment on the left magnet and the right magnet according to the required value of the background magnetic field and then perform effective separation on ores after canceling the magnetizing power source when in work, and can perform demagnetizing treatment on an upper magnet and a lower magnet when in assembly and maintenance so as to solve the magnetic blockage problem. The high gradient magnetic separator can greatly reduce the energy consumption, and fully ensure convenient maintenance in practical production.