The invention provides a chemical plating and a preparation method and application thereof. The chemical plating comprises a base material layer, a first plating and a second plating which are arrayedin sequence. The first plating is a Ni-P-Cu layer. The second plating is a Ni-P-Cu-TiO2 layer, wherein the second plating comprises 3-5 gradient layers with increasing TiO2 concentration in the direction of the base material layer to the second plating. All plating layers are electroplated on the surface of the pretreated base material layer in sequence. The TiO2 concentration gradient layers areobtained by electroplating in plating baths with different TiO2 concentrations. The chemical plating can be applied to a heat exchanger, and is used as the surface condensation heat exchange plating.According to the TiO2 in the plating layer, the surface of the plating is hydrophobic, and the heat exchange efficiency of the heat exchanger is improved. According to the TiO2 gradient layers, the bonding force between TiO2 particles and the surface of a matrix is strengthened, the internal stress between the platings is reduced, the wear resistance and corrosion resistance of the plating are improved, and the plating is not prone to falling off.