Abstract: The diffusion connection between tungsten and steel in tritium breeding blanket was successfully achieved by indirect welding and hot isostatic pressing, using low radioactive pure chromium as the interlayer materials, and the microstructure and mechanical properties of the welding interfaces were analyzed. The results show that the tungsten/chromium/steel interfaces are well connected after welding, and no obvious pores and cracks are found. The tungsten/chromium interfaces are distinct, and no intermediate phases appear. The chromium/steel interfaces form the obvious banded intermediate phase (Cr₇C₃) and columnar crystal solid solution (α-Fe, Cr). Due to the high brittleness of hot-pressed pure chromium sheets as the interlayers, the microhardness of tungsten/chromium and chromium/steel interfaces is HV 187.0 and HV 140.0, respectively, which is significantly lower than that of pure tungsten and steel, and the tensile strength is very low, only about 15 MPa.