A manufacturing method of a platinum complex is mixing chloroplatinic acid and a chelating agent with a solvent, wherein [PtCl6]2− ions of the chloroplatinic acid is reacted with the chelating agent to form a platinum complex Pt[R]2+, wherein the chelating agent(R) is selected from ethylenediamine , 1,10-phenanthroline, 2,2′-Bipyridine, diethylenetriamine, triethylenetetraamine, phenanthroline, or bipyridine. Moreover, a method for producing a platinum catalyst on supports is mixing the chloroplatinic acid, a chelating agent and supports with a slovent to form a platinum complex, which is incorporated onto the supports. Following, a reduction step and a drying step are processed to get the platinum catalyst on the supports.