Abstract: Gradient-structured tungsten heavy alloys with spatially graded mechanical properties can effectively resolve the strength-ductility trade-off in conventional homogeneous tungsten alloys. The high-strength 93W–Ni–Fe–Mo alloys and high-ductility 90W–Ni–Fe–Co alloys were separately developed through the optimized design. The co-sintering was employed to fabricate the gradient-structured tungsten alloys, and the microstructural characteristics and mechanical properties of the W–Ni–Fe–Mo/Co alloy systems and the W–Ni–Fe gradient-structured alloys were systematically investigated. In the results, the addition of Mo can effectively improve the tensile strength of 93W–Ni–Fe alloys and the introduction of Co can improve the ductility of 90W–Ni–Fe alloys. Being fabricated by integrated pre-sintering and stepwise sintering at 1480 ℃, the gradient tungsten alloys show about 20 μm interfacial layers. Tensile tests reveal the 1153.0 MPa strength (13.1% elongation) in the high-strength zone and the 972.6 MPa strength (21.5% elongation) in the high-ductility zone. The grain refinement and solid solution strengthening mechanisms are induced by Mo doping, however, the introduction with high content (Mo mass fraction≥12%) can lead to the formation of MoNi intermetallic compounds at the W/γ binder phase interface, which can damage the plasticity.