The evolution mechanism of the weld zone microstructure and the room temperature tensile strength of the weldment for Ti2AlNb/TC11 dissimilar alloy were investigated through changing the isothermal deformation parameters. Results show that at lower strain rate with higher deformation, the grain refinement of the welded interface is related to dislocation cutting across grain boundary and intragranlar strip O/α2-phase and elongated O/α2-phase necking down. With low deformation, the grain refinement is only related to dislocation cutting across the grain-boundaries and transgranular strip O/α2-phases. Appearance of course and fine strip O/α2-phases is related to response of dynamic recrystallization at low strain rate (10-4 s-1) and high strain rate (10-2 s-1). After hot deformation at 980 °C, at strain rate of 10-2-10-4 s-1 and deformation of 30%-50%, the room-temperature strength of the Ti2AlNb/TC11 dual-alloy joint is better than that of TC11 alloy