A high-frequency transformer, comprises: a ring core made of amorphous magnetic material; a core protection box made of conductive material and enclosing the ring core; and a high-voltage winding, consisting of enamel-insulated wire wound on the core protection box. Wherein, on the ring top wall of the core protection box there is a ring gap in the peripheral direction, and at inner fringe and outer fringe of the ring gap, a plurality of leading wires are respectively arranged in the peripheral direction. The leading wires at inner fringe and outer fringe of the ring gap are electrically-connected together respectively and form two terminals. The core protection box and the two terminals constitute low-voltage winding of the high-frequency transformer. If the low-voltage winding comprises two or more core protection boxes, it can have a central tap or have multi-turn. A thus fabricated high-frequency transformer has a smaller size, a lighter weight and is more apt to industrial batch manufacture. Further, the magnetic coupling between the high-voltage winding and the low-voltage winding can be increased.