The invention discloses a nano chemical plating and a preparing method and application thereof. The plating comprises a base material layer, a first plating body and a second plating body which are sequentially arranged, the first plating body is a Ni-P-Cu layer, the second plating body is a Ni-P-Cu-TiO2 layer, the concentration of the TiO2 is increased to 3 to 7% from zero in the direction from the base material layer to the surface layer of the second plating body, and is linearly increased, according to the nano chemical plating, all plating bodies are chemically plated on the surface of the pre-treated base material layer in sequence, and the concentration of the TiO2 is linearly increased. The nano chemical plating can be applied to a heat exchanger and can serve as a surface condensation heat exchange plating, the plating contains the TiO2, and the surface of the plating is lyophobic, heat exchange efficiency of a heat exchanger is improved, and due to linear increasing of the TiO2 concentration, combination force between the TiO2 particles and the surface of a base body is increased; internal stress between the plating bodies can be reduced, wear resistance and corrosion resistance of the plating bodies can be improved, and the plating bodies are not prone to falling.