Abstract: The effect of different Al content on the microstructure and mechanical properties of the CoFeNiVAl_x（x=0-1）high-entropy alloys was studied by X-ray diffractometer（XRD）, scanning electron microscope（SEM）, electron back-scattered diffraction（EBSD） and universal testing machine, etc. The results show that the addition of Al element promotes the formation of BCC phase, and the microstructure changes from columnar grains to equiaxed grains. The FCC +BCC two-phase structure greatly improves the yield strength of the alloy and retains excellent plasticity at the same time. Among them, CoFeNiVAl_0.5 alloy possesses a high yield strength of 1272 MPa and a plastic strain of 32%.