The invention relates to a sulfur hexafluoride (SF6) gas insulated traction transformer in an auto-transformer (AT) power supply mode and belongs to the technical field of transformers. The invention adopts the technical scheme that: the transformer comprises a gas tank (1), coils (8), a transformer body insulator (9), an iron core (10), leads (7), a cooling device (6), a temperature controller (4), a body gas density meter (3) and a burst pressure relay (5), wherein the temperature controller, the body gas density meter and the burst pressure relay serve as safety protection devices of the transformer and can monitor temperature, pressure and the like of the transformer in real time. By the technical scheme of the invention, a winding pair, of which main fluxes generated on each core column have the same direction and two magnetic leakage groups are subtracted from each other, is formed, so that a low-impedance requirement is met in the limited height of windings. In a radiation modeof SF6 gas cycle cooling, a relatively high fire protection requirement is met, the condition of small occupied area is also met, and excellent economic benefit and excellent social benefit are realized generally.