Abstract: To achieve the metallurgical connection of tungsten and steels in the tritium breeding blanket, the diffusion connection of tungsten and steels was successfully realized by hot isostatic pressing as the indirect welding method, using pure chromium with low radioactivity as the interlayer material. The microstructure and mechanical properties of the welding interface were analyzed. The results show that the tungsten/chromium/steel interface is well connected after welding, and no obvious pores and cracks are found. The tungsten/chromium interface is distinct, and no intermediate phase appears. The chromium/steel interface forms the obvious banded intermediate Cr₇C₃ compound phases and the columnar crystal morphology (α-Fe,Cr) solid solution. Due to the hot-pressed pure chromium sheets with high brittleness as the interlayer, the microhardness of tungsten/chromium and chromium/steel interfaces is HV 187 and HV 140, respectively, which is significantly lower than that of pure tungsten and steels, and the tensile strength is very low, only about 15 MPa.