In this paper, based on the CoCrNi medium-entropy alloy with equal atomic ratio, the CoCrxNi (x=1.0, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0) medium-entropy alloy was prepared by a vacuum arc melting furnace, and the effect of Cr element content on the alloy microstructure was studied. The influence of organization and mechanical properties. The results show that CoCrxNi (x=1.0, 1.5, 1.6) medium-entropy alloy is a single face-centered cubic phase (FCC); With the increase of Cr content, Cr rich strip structure of body centered cubic phase precipitated in FCC phase matrix of entropy alloy in CoCrxNi (x=1.7, 1.8, 1.9, 2.0) medium-entropy alloy; the strength and hardness of the alloy continue to increase with the increase of the Cr element content, but the plasticity deteriorates; compared with the equal atomic ratio CoCrNi medium entropy alloy, While maintaining high plasticity, the strength and hardness of CoCr1.7Ni medium-entropy alloy are significantly improved.