In this paper, a series of new Cr-Mn-Fe-V-Cu high-entropy alloys with high ductility were prepared by arc melting and suction casting. It was found that with the addition of Cu, the structure of the alloys evolved from BCC+BCC1 phases (CrFeMnV alloy) to BCC + FCC phases (CrFeMn_xVCu_0.2xalloys). Formation of the Cu-Mn-rich FCC phase was caused by immiscibility of Cu with V, Cr and Fe. With increase of Cu, the volume fraction of FCC phase increased, and the morphology of the FCC phase transformed from granular particles to long strips and blocks. The five Cr-Mn-Fe-V-Cu HEAs present a great balance between strength and ductility. The CrFeMn0.3VCu0.06 alloy with granular FCC particles exhibits highest compressive yield strength (1273 MPa) and excellent ductility (ε_f = 50.7%). The dislocation and precipitate strengthening are responsible for high strength of the CrFeMn0.3VCu0.06 alloy. Therefore, the dislocation density and distribution of FCC phase are the crucial factors influencing both microstructures and mechanical properties of the HEAs.