Objective To improve the abrasion resistance of the surface on cast iron by plasma alloying high entropy alloy coating process. Methods High entropy alloy coating was prepared on the surface of HT250 cast iron by plasma alloying Al, Co, Cr, Cu, Mn and Ni powders in equal molar ratio. The microstructure of the coating was studied by SEM, EDS, XRD, and its microhardness distribution was tested by the microhardness tester. Results Due to melting of a small amount of iron, the atoms such as Fe and C dissolved into the coating to get AlCoCrCuFexMnNiCx, the thickness of which was about 0. 2 mm. The mixing entropy of both the composition and the microstructure of the coating distributed in a high-medium-low gradient. The microstructure of the coating was mainly composed of high-entropy alloy dendrite and interdendrite cementite and σ phase etc, and the coating contained mainly FCC, BCC, Fe3 C and σ phase. The microhardness of the coating was about 350 ~ 600HV0. 2, which was significantly higher than that of the matrix (200 ~ 230HV0. 2). Conclusion The composite coating including high entropy alloy and carbide could be formed on the surface of cast iron by plasma alloying, which improved the microhardness of the cast iron, and thus helped to improve the abrasion resistance of the surface on cast iron.