NiCoFeCuCr high entropy alloy coatings were in-situ synthesis on the cooper surface using mechanical alloying(MA) method. The phase composition and microstructure of the coatings were characterized using X-ray diffraction(XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy(EDS). The microstructure and the formation mechanism of the coatings were studied. It is revealed that increasing of milling time can enhance the thickness and densification of the coating. The most dense and uniform coating, with an average thickness of 40μm, were synthesized after MA for 5h, which metallurgically bonding with the copper substrate. The formation of the coating can be simpli?ed as follows:(1)Particles hammered into substrate. (2)Powder deposited on substrate through cold welding. (3)Diffusion between theScoating andSthe substrate. (4)Work hardening leading to spalling fatigue.