Mictrostructure and formation mechnaism of Fe/Ai/Cr8-Ni8 joint, which was obtained by diffusion-bonding with 1333K for 3.6ks at a pressure of 17.5 MPa, were analyzed by means of Scanning electron microsocopy (SEM), Electron probe microanalysis (EPMA) and X-ray Diffraction (XRD). The results indicated that new phase including feAl,Ni and a-Fe (Ai) solid solution were formed during the diffusion bonding of Fe3 Al intermetallic to Cr18-Ni8 steel. And the microstructure of diffusion-bonded Fe2Al/Cr18 Ni8 joint is Fe3/Al (Fe3Al+FeAl)Ni3 Al/a-fe(Al)/Cr18-Ni8.