Objective To investigate the annealing age hardening of Al3CoCrCu1/2FeMoNiTi high-entropy alloy coating and strengthening mechanism. Methods Al3CoCrCu1/2FeMoNiTi high-entropy alloy coating was deposited on 40Cr steel with laser cladding equipment, and then was annealed. X-ray diffractometer, scanning electron microscope and microhardness tester were employed to analyze microstructure and hardness. Results The original coating was of BCC single-phase structure. After annealing at 300 ℃ and 500 ℃, the coating was still of BCC structure. The coating annealed at 700 ℃ precipitated NiTi intermetallic compound phase. When the annealing temperature was 900 ℃, the coating was composed of FCC phase and NiTi. The coating SEM morphology that was annealed at 0~700 ℃ was granular. After annealing at 900 ℃, the morphology was like lath. The coating annealed at 300 ℃ had a lower hardness than that of non-annealed. The hardness increased when the annealing temperature was more than 300 ℃. It reached the highest about 924HV at 700 ℃. It then became lower at 900 ℃. NiTi phase precipitating improved the alloy hardness. Solid solution strengthening of high-entropy alloys could be explained by dislocation strengthening mechanism. Conclusion Al3CoCrCu1/2FeMoNiTi high-entropy alloy coating obviously shows age hardening effect. The alloy coating has the best hardness after annealing at 700 ℃.