90W–Ni–Cu–Sn alloy/steel composite structure has been fabricated by co–sintering process at temperature as low as 1200 °C for 3 h using hot isotactic pressing (HIP). Microstructural studies revealed that a rich Ni, Cu and Sn transition layer was formed at the co–sintering interface due to the liquid γ–(Ni, Cu, Sn) migration, and no intermetallic compounds or other brittle phases were found at the interface. The shear tests indicated that the average shear strength of the co–sintered 90W–Ni–Cu–Sn/steel joint could reach 382.9 MPa. This successful attempt provides a new idea for the fabrication of tungsten alloy/steel composite structure component.