AlxFeCoNiB0.1 (x=0.4, 0.5, 0.8, 1.2, 1.6where, x is the mole percentage) were prepared by vacuum arc melting.The microstructure and mechanical property of AlxFeCoNiB0.1 high-entropy alloys were investigated. With the increase of Al content, the cast dendrites of the alloy were changed from FCC phase to B2 (AlNi) /BCC phase. When x= 0.4 and 0.5, the microstructures of the alloy were consisted of the dendrite FCC phase and the interdendritic B2 phase and (Fe, Co) 2B; when x=0.8, the dendrites were composed of B2 phase, and the interdendrites were composed of FCC phase and (Fe, Co) 2B; when x=1.2, the interdendritic structures were consisted of the eutectic FCC+ (Fe, Co) 2B, and the nanoscale granulars are the BCC phase;When x=1.6, the eutectic structures disappeared. With the increase of Al content, the compressive strength increased first and then decreased. When the content of Al was 0.8, it reached the peak value of 2243MPa. Appropriated amount of Al can improve the comprehensive mechanical properties of high entropy alloy。