Cu 0.5 FeNiVAl x high entropy alloys have been designed and prepared to study the microstructure and mechanical properties in as-cast and heat treated states. The as-cast Cu 0.5 FeNiV alloy is mainly composed of fcc and σ phases. With the increase in Al, the phase composition gradually changes to the fcc + bcc structure. In the Cu 0.5 FeNiVAl x alloy system, the compressive strength (1 801 MPa) of Cu 0.5 FeNiVAl 0.5 alloy is the best, and the Cu 0.5 FeNiVAl 1.2 alloy has the highest hardness (694 HV). In order to improve its strength, the Cu 0.5 FeNiVAl 0.5 alloy was annealed at 500 °C, 750 °C and 1 000 °C for 10 h, respectively. The highest compressive strength (2 154 MPa, increased by 20 % compared to the as-cast state) is reached at 750 °C annealing temperature. Meanwhile, the microhardness is increased from 516 HV to 670 HV, an increase of 30 % relative to the as-cast one. Study of the heat treatment process on the mechanical properties of high-entropy alloys contributes to the transformation of these materials from the laboratory research stage to the practical production stage.