The utility model relates to a transformer body. The transformer body comprises a three-dimensional wound core, a coil, a pressing assembly and a tensioning assembly. The three-dimensional wound corecomprises a single-frame core. And the coil is wound on the single-frame iron core. The pressing assembly comprises an upper clamping piece and a lower clamping piece. The upper clamping piece and thelower clamping piece are installed at the two ends of the three-dimensional wound core respectively, and the upper clamping piece and the lower clamping piece abut against the coil. The tensioning assembly comprises at least two insulating pull belts which are arranged in parallel at intervals. The two ends of the insulating pull belt are fixedly connected with the upper clamping piece and the lower clamping piece respectively so that the coil can be clamped between the upper clamping piece and the lower clamping piece. Due to the fact that the insulation pull belt has the electric insulationperformance, the insulation pull belt can be infinitely close to the coil and even attached to the coil, the area of the upper clamping piece and the area of the lower clamping piece used for fixingthe insulation pull belt in the direction perpendicular to the axis of the three-dimensional wound core are small, and the size of the transformer body is small. Therefore, the volume of the three-dimensional wound core oil-immersed transformer comprising the transformer body is relatively small.