Abstract: CoFeNiCrMnB_<i>x high entropy alloy is prepared by vacuum arc melting furnace and annealed. The results show that when the CoFeNiCrMnB_0.15 and CoFeNiCrMnB_0.20 alloys are annealed at 1 100 ℃ for 20 hours, their interdendritic structures are granular Cr₂B phase, and that the granular Cr₂B phase increases with the increase of B content. The yield strength and tensile strength of CoFeNiCrMnB_0.20 alloy are 496 MPa and 890 MPa, which are 104.0% and 79.4% higher than those of the as cast CoFeNiCrMn alloy.