FeCrCoNiMnBx (x=0, 0.05, 0.1, 0.15, 0.2 where, x is the mole percentage) were prepared by vacuum arc melting.The microstructure and mechanical property of FeCrCoNiMnBx high-entropy alloys were investigated.The results show thatwithout boron addition, the alloy is composed of simple fcc solid solution structure and the cellular crystal structures form . When the content of B in the alloys was higher than 0.05, (Fe, Co) 2B with shape of dendritic and nano granular can be observed. With the increase of B content, the tensile strength of the alloy increases gradually. When the content of boron is 0.2, the tensile strength of the alloy is 610 MPa, but the elongation is only 7%. The proper amount of B element can improve the comprehensive mechanical properties of high entropy alloy.When the content of B is 0.1, the tensile strength is 550 MPa, and the elongation is 20%._{proper amount of B element can improve the comprehensive mechanical properties of high entropy alloy.When the content of B is 0.1, the tensile strength is 550 MPa, and the elongation is 20%.}