The microstructure and mechanical properties of AlxCoCrCuFeNi with different Al content have been studied. The results showed that the microstructures exhibit simple dendrite and interdendrite structures. When the content of aluminum was low, the alloy was composed of a simple FCC solid-solution structure. As the aluminum contents increasing, a BCC structure appeared. The high entropy effects and sluggish diffusion enhance the formation of simple solid-solution phases and submicron structures with nanoprecipitates in the alloys. With the addition of aluminum from x=0 to 3.0, the hardness of the alloys increase from 1530 to 7350 MPa Correspondingly, the alloy’s deformability falls and transfers from ductile materials to brittle materials at moderate temperatures.