The invention relates to a preparation method of metal mono-atoms and belongs to the technical field of materials science and engineering. The metal mono-atoms prepared through the method may include: Pt, Ag, Au, Pd, Rh, Ir, Ru, Co, Ni and Cu, and metal mono-atoms supported on TiO2, zinc oxide, cerium oxide, aluminum oxide, silicon oxide, ferric oxide, manganese oxide, C3N4, mesoporous carbon, ultrathin carbon films, graphene, carbon nano tubes or molecular sieve materials, etc. The method includes the steps of: preparing a precursor solution in a certain concentration, and freezing the solution; and under an ice phase, processing ice cubes by means of external field or reaction between reactants in the ice cubes, and when the ice cubes are molten, a mono-atom solution is finally produced; mixing the mono-atom solution with different materials, performing ultrasonic treatment, filtration, cleaning and drying to finally obtain the mono-atoms supported on various materials. The preparation method is quick, has high product density, allows mass production, is high in efficiency and has wide application range, and compared with a co-precipitation method and an impregnation method, the method has significant advantages.