The invention relates to a method for manufacturing a radiator with radiating fins and a structure of the radiator, wherein the manufacturing method comprises the following steps: providing a substrate which comprises a base and a plurality of extending arms, and making clearance exist between each extending arm and other two extending arms adjacent to the extending arm; and providing a pluralityof radiating fins, and inserting the radiating fins into the clearance between the extending arms corresponding to the substrate, wherein each radiating fin comprises a base sheet and two heat sinks,and the two heat sinks of each radiating fin are inserted into the clearance between the corresponding extending arm and the other two extending arms adjacent to the extending arm; and bending and pressing Each extending arm of the substrate to make one side wall surface of both opposite side wall surfaces forming each extending arm closely butt against one surface of both opposite surfaces forming each heat sink. The method has the advantage of avoiding losing thermal conduction.