A manufacturing method for a radiator and a structure thereof are disclosed. The manufacturing method for a radiator includes the following steps. A substrate and a plurality of cooling sheets are provided. The side wall of the substrate has a plurality of concave troughs. The cooling sheets are respectively plugged into the concave troughs. The two side walls of each of the concave troughs tightly contact the two opposing surfaces of the cooling sheet. Thereby, each of the cooling sheets is located at the side wall of the substrate, and the top portion and the bottom portion of the cooling sheet extend to outside of the top surface and the bottom surface of the substrate. By using the riveting technology to directly fasten the cooling sheets via the two side walls of the concave troughs, the present invention prevents the heat-conduction loss from being occurred.