The inventing belongs to the field of transformer fabrication and specifically relates to a novel three-phase generator transformer with ultra-high capacity and high voltage. A boosting seat at the high-voltage outlet terminal of the transformer is turned at 5-15 DEG angle to the side away from the transformer. An oil reservoir is positioned above the master oil tank of the transformer in a way that the longitudinal direction of the oil reservoir is parallel to the long axis of the oil tank. An insulating paper plate is provided between the contact surfaces of the upper/lower iron core fasteners and the iron core of the transformer, thereby completely isolating the upper/lower iron core fasteners, and the upper/lower iron core fasteners are connected with the iron core by grounded wires, thereby allowing the upper/lower iron core fasteners to be grounded individually. A fastener magnetic shield is fixed on the ventral plate of each of the upper/lower iron core fasteners of the transformer by using a two-way screw bolt. A limb plate of the upper iron core fastener of the transformer is retracted inside the fastener. A suspended ring on the ventral plate of the upper iron core fastener is covered with a Cu shield on the outer surface. An iron yoke block is provided between the coil and the lower part of the oil tank inside the transformer and is provided thereon with an elongated fan-shaped oil inlet/outlet, the oil inlet/outlet being positioned above the exit of the oil tank.