Abstract: Here, we architected a duplex heterostructure with FCC/L1₂ and B2 phases in Ni₄₉Fe₂₈Al₁₇V₆ eutectic high-entropy alloy (EHEA) by thermal-mechanical process. Ultra-high yield strength of ∼1550 MPa, high tensile strength of ∼1772 MPa and good ductility of ∼16.5 % at room temperature (298 K) were exhibited. Particularly, ultra-high yield strength of ∼1877 MPa, ultra-high tensile strength of ∼2157 MPa and uniform elongation of ∼10 % were achieved at cryogenic temperature (77 K). Such excellent room-temperature mechanical properties are attributed to the hetero-deformation induced (HDI) hardening. Ultrahigh cryogenic-temperature strength originates from not only HDI hardening, but also the strong interaction of deformation twins and high-density dislocations.