The invention relates to a method and a device for increasing the output power of a transformer. The device mainly comprises two or more metal briquettes, magnetic cores, column cores, coils, conductive objects and insulating objects, wherein each briquette is provided with an arc groove and a semi-circular column core; two or more metal briquettes, which are in isolated connection to form a whole body through the insulating objects, can be used as a secondary coil or a transformer protection box, and can be spliced to form two or more circular grooves or two or more circular column cores; the circular column cores in the circular grooves can be sleeved with annular magnetic cores made of a nano-metal material; and primary coils wind the magnetic cores. A screw hole connected with the corresponding conductive object is formed in the end face of each metal briquette, and a liquid circular cooling and heat-dissipating pipeline is arranged inside each metal briquette.