The three-phase oil-immersed transformer adopts fully filled and sealed corrugated oil tank. The oil tank shell adapts to the expansion performance of the oil with its own elasticity and meets the heat dissipation requirement.The body of the device adopts a new insulation structure. which improves its ability to withstand short circuit; the iron core is made of high-quality cold-rolled silicon steel sheet; both high and low voltage windings are made of oxygen-free copper wire and adopt multi-layer cylindrical structure: all fasteners are treated with special anti-loosening measures. with vacuum drying, vacuum oil filtration and oil injection process.