A transformer tank with a system for preventing a rupture of the transformer tank, which system is provided on the transformer tank and prevents a rupture of the transformer tank due to a sudden rise in pressure in the transformer tank, the system comprising: a support part and a shielding plate installed in the transformer tank, the support part supporting the shielding plate for absorbing a magnetic field so that the shielding plate is not directly attached to the transformer tank; a plurality of rupture discs and a plurality of pipes extending outwards from the transformer tank, the plurality of rupture discs mounted, respectively, to the plurality of pipes extending outwards from the transformer tank, and ruptured when pressure in the transformer tank reaches a predetermined pressure level, thus opening passages of the plurality of pipes; a plurality of relief tanks vertically installed at a position neighboring the transformer tank, and coupled respectively to the plurality of pipes, thus providing space for storing insulating oil; and an oil gauge mounted at a lower position in each of the plurality of relief tanks, and generating a signal when the insulating oil flows into a relief tank of the plurality of relief tanks, thus informing a manager of rupture of each of the rupture discs and discharge of the insulating oil; wherein the shielding plate is welded to a front surface of the support part, and the support part has a plurality of pressure transmitting holes,, each at a position corresponding to a pipe of the plurality of pipes, so that the pressure in the transformer tank is transmitted to a respective rupture disc of the plurality of rupture discs, four corners of the support part being bent backwards a predetermined length, thus providing welding parts welded to an inner wall of the transformer tank. a support part and a shielding plate installed in the transformer tank, the support part supporting the shielding plate for absorbing a magnetic field so that the shielding plate is not directly attached to the transformer tank; a plurality of rupture discs and a plurality of pipes extending outwards from the transformer tank, the plurality of rupture discs mounted, respectively, to the plurality of pipes extending outwards from the transformer tank, and ruptured when pressure in the transformer tank reaches a predetermined pressure level, thus opening passages of the plurality of pipes; a plurality of relief tanks vertically installed at a position neighboring the transformer tank, and coupled respectively to the plurality of pipes, thus providing space for storing insulating oil; and an oil gauge mounted at a lower position in each of the plurality of relief tanks, and generating a signal when the insulating oil flows into a relief tank of the plurality of relief tanks, thus informing a manager of rupture of each of the rupture discs and discharge of the insulating oil; wherein the shielding plate is welded to a front surface of the support part, and the support part has a plurality of pressure transmitting holes,, each at a position corresponding to a pipe of the plurality of pipes, so that the pressure in the transformer tank is transmitted to a respective rupture disc of the plurality of rupture discs, four corners of the support part being bent backwards a predetermined length, thus providing welding parts welded to an inner wall of the transformer tank.