The method includes steps: removing insulation on header of 10KV cable; using hydraulic tongs to fix copper connection nose on bare copper wire through cold pressing; insulator is fixed on clamping piece of transform through full screw; tapping plate and insulator is locked fixedly through screw and screw hole on insulator. Tapping leads in high voltage is prepared through following operations: fixing connector in high voltage by bolt; connecting connection straps to rated voltages; fixing lead out wire between XB phases as well as between YC phases to wiring board; passing through inside insulating rod, the lead out wire between AZ phases is fixed on the wiring board by using hexagonal copper bar. Advantages are: constant distance between lead out wires and no burr without need of packaging so as to reach purpose of safe.