To introduce D0₂₂ superlattice (noted as γ′′ phase) precipitation strengthening in additive manufacturing, a design strategy of combining the overall valence electron concentration with the calculation of phase diagrams is proposed, and Ni_2.1CoCrFe_0.5Nb_0.2 HEA is designed. The wall-shaped samples were prepared by AM, and after solution at 1100 °C for 2 h and aging at 650 °C for 120 h, the γ′′ phase with volume of 14% causes yield strength increase by 727 MPa, the yield strength increased dramatically to ∼1005 MPa, the ultimate strength increased dramatically to ∼1240 MPa, the tensile elongation maintained at ∼20%. The high strength results from the precipitation strengthening of the γ′′ phase, and the large ductility are primarily attributed to an evolution of multiple stacking fault structures. The present study will not only promote the development of high-performance HEAs by AM but also provides a pathway for achievement of AM technology industrial applications.