Intermetallics TiAl was diffusion-bonded to steel 40Cr in vacuum furnace with interlayer V/Cu. The results show that infinite sosoloid that made for bond performance is formed at the interface of V/Cu and Cu/40Cr, and three acting layers are formed at the interface of TiAl/V including Ti 3Al layer at TiAl side, intermittent V 5Al 8 layer in the middle and Ti-V sosoloid at V side. Fragile reactors V 5Al 8 arising at the interface lead to bad performance of joints, and the strength of the joint is 200 MPa, while it was still higher than the strength of the joint intermetallics TiAl to 40Cr steel diffusion-bonded directly. Intermetallic TiAl and 40Cr steel are diffusion-bonded successfully by using a composite isolation layer V/Cu. Intermetallics TiAl was diffusion-bonded to steel 40Cr in vacuum furnace with interlayer V / Cu. The results show that infinite sosoloid that made for bond performance is formed at the interface of V / Cu and Cu / 40Cr, and three acting layers are formed at the interface of TiAl / V including Ti 3Al layer at TiAl side, intermittent V 5Al 8 layer in the middle and Ti-V sosoloid at V side. Fragile reactors V 5Al 8 arising at the interface lead to bad performance of joints, and the strength of the joint is 200 MPa, while it was still higher than the strength of the joint intermetallics TiAl to 40Cr steel diffusion-bonded directly. Intermetallic TiAl and 40Cr steel are diffusion-bonded successfully by using a composite isolation layer V / Cu.