The invention discloses a high-power planar transformer, which comprises a transformer body, wherein a first groove is formed in one side of the transformer body; a second groove and a cylinder are arranged in the other side of the transformer body; first round holes are formed in two sides of the cylinder; a fixed rod is connected to the inside of the first round holes in a sliding manner; a compression spring is arranged at the connected part of the fixed rod and the cylinder; one end of the compression spring is connected with the inner wall of the cylinder and the other end of the compression spring is connected with a gasket; the gasket is connected with the cylinder in the sliding manner; a clamping post is arranged below the cylinder and is located on the inner wall of the transformer body; an opening is formed in the top part of the transformer body; a cover body is arranged in the opening; one side of the cover body is hinged with the transformer body; a buckle is arranged at the bottom part of the cover body and is matched witch the fixed rod and the clamping post respectively; and a fixed post is arranged on the inner wall of the transformer body. The high-power planar transformer is simple in structure, relatively low in cost, economical, practical and small in occupied space.