Abstract: In order to investigate the influence of high magnetic heat treatment on interfacial microstructure and properties of TiAl/Ti₂AlNb diffusion bonding joint, the interfacial microstructures and mechanical properties of TiAl/Ti₂AlNb diffusion bonding joints are analyzed after heat treatment with and without high magnetic field. Results show that both the two kinds of heat treatment can eliminate the brittle phase in the interface. The heat treatment with high magnetic field can refine the recrystallized grains in the bonding interface, the brittle α₂ phase near the TiAl alloy is distributed depressively, the precipitated O phase near the Ti₂AlNb alloy is fine and needle-like, and the β₀/B2 and O phases interdiffuse at the interface. The heat treatment with high magnetic field can help to eliminate the metallurgical interface and improve the strength and plasticity of the joint. The tensile strength and percentage elongation after fracture of the joint after heat treatment with high magnetic field are 268.76 MPa and 0.160%, respectively, which increase by 54% and 202% compared with those of the heat treatment without magnetic field. High magnetic can accelerate the interfacial element diffusion, promote the interfacial metallurgical reaction, improve the interfacial metallurgical bonding, and strengthen the mechanical properties of TiAl/Ti₂AlNb joint. This method can be used to the regulation of microstructures and mechanical properties of other welded joints or functionally graded materials.