CrNiAlCoMoB0.5high-entropy alloy (HEA) is prepared on 45# steel bylaser cladding. The microstructure and corrosion resistance properties of this HEA coating are studied. The results show that the corrosion resistance properties of the HEA are remarkable, corrosion electric potential Ecorr and corrosion currect Icorr of CrNiAlCoMoB0.5HEA are equal to those of 304 stainless steel in 3.5%NaCl (mass fraction) while the resistance to pitting is better. Compared with 304 stainless steel, the ability of passivating of HEA coating is weaker. In 1 mol/L H2SO4 electrolytic solution, the Ecorr and Icorr of HEA coating and 304 stainless steel are in an order of magnitude, which means corrosion resistance of CrNiAlCoMoB0.5 coating is remarkable. Corrosion behavior of the HEA coating is intergranular corrosion while 304 stainless steel is irregular flake corrosion. In 1 mol/L NaOH electrolytic solution, Ecorr of CrNiAlCoMoB0.5HEA coating is lower than that of 304 stainless steel, which shows that the tendency of corrosion is larger. Meanwhile, Icorr of the HEA coating is smaller, the corrosion resistance of CrNiAlCoMoB0.5HEA coating is better, and the ability of passivating is equal to that of the 304 stainless steel.