The invention provides a preparation method of an in-situ synthesis low-pressure cold spraying CuNiCoFeCrAl2.8 high-entropy alloy coating. The method comprises the following steps that Cu powder, Ni powder, Co powder, Fe powder, Cr powder and Al powder are uniformly mixed to obtain powder for cold spraying, and then low-pressure cold spraying is carried out on the surface of a metal matrix so as to obtain a mixed powder coating, and then induction remelting in-situ synthesis is carried out to obtain the CuNiCoFeCrAl2.8 high-entropy alloy coating. According to the method, the low-pressure coldspraying technology is used, the cold spraying powder is subjected to low-pressure cold spraying on the matrix, the induction remelting in-situ synthesis is carried out, the CuNiCoFeCrAl2.8 high-entropy alloy coating is obtained, an alloying reaction is sufficient, the microstructure of a mixed powder coating forms a high-entropy alloy structure with a body-centered cubic structure from a pure metal in situ, the high-entropy alloy coating is formed, the structure is compact, the porosity is low, the high-entropy alloy structure is stable in structure, few in impurities, excellent in mechanicalperformance, high in strength and high in hardness, and good in wear resistance and corrosion resistance; and the thickness of the CuNiCoFeCrAl2.8 high-entropy alloy coating is 100 microns-3 millimeter, the preparation equipment is simple, and the process is convenient.