The invention discloses an adjustable transformer fixing holder, comprising a mounting beam, wherein a plurality of groups of mounting holes are arranged on the mounting beam; each group of mounting holes are composed of two elliptical holes which are arranged along the same direction. A cup head square neck bolt for fastening a transformer is assembled in each elliptical hole. The center distance of two elliptical holes is equal to the mounting hole distance of the transformer; the length of each elliptical hole is greater than the aperture of each mounting hole of the transformer; the width of each elliptical hole is greater than the width of the square neck of the cup head square neck bolt and is smaller than the diameter of a cup head; and fastening openings are arranged at two ends of the mounting beam. The adjustable transformer fixing holder is simple in structure and ingenious in design and is applicable to fixing and mounting of current transformers or voltage transformers of various models; the time and labor are reduced; and the integrated mounting finishing progress of a control cabinet is greatly improved.