The invention relates to a method for manufacturing the wound core of a triangular wound core transformer and a product. The method comprises the following steps of: more reasonably combining the arrangement modes of cores; splicing three identical single frames to form a three-dimensional equilateral triangular core; winding coil stock into a core single frame by using a three-dimensional wound core winder; dividing a three-dimensional wound core into three single-frame cores and respectively winding, wherein each single frame is formed by continuously winding a plurality of trapezoid tapes with constantly changing widths; and splicing to form the three-dimensional wound core according to a three-dimensional equilateral triangle. After the spliced core is subjected to splicing and annealing treatment again, the three-phase core magnetic circuit of the product is completely symmetrical, magnetic resistance is greatly reduced and excitation current and no-load loss are obviously reduced. The wound core transformer has the advantages of lower running noise, more compact structure, high efficiency, energy and material conservation, low cost and high performance.