Abstract: In order to realize the metallurgical connection between tungsten and steel in tritium breeding blanket, this paper adopts indirect welding method, using low radioactive pure chromium as the interlayer material, and successfully achieves the diffusion connection between tungsten and steel by hot isostatic pressing. 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 an obvious banded intermediate phase Cr7C3 compound and a columnar crystal morphology (α-Fe, Cr) solid solution. Due to the application of hot-pressed pure chromium sheet 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 steel, and the tensile strength is very low, only about 15 MPa.