The high-temperature mechanical properties and deformation behaviors of TiAl-base alloys prepared by severe plastic deformation-reactive sintering were investigated. The nanocrystalline TiAl-base alloys were obtained with Ti and Al powders mechanically milled, consolidated by warm extrusion and then reaction sintered. The results show that after warm extrusion at 250℃ (extrusion ratio 16), presintering at 630℃ for 2 h and high-temperature sintering at 1250℃ for 4 h, the Ti/Al composite powder can be prepared into fully dense TiAl-base alloys. Such alloys have fine and homogenous microstructures with small grain sizes of 5-10 μm, and their compressive yield strength at 800℃ can reach 620 MPa, exhibiting superplasticity. Accordingly, the influence of microstructure on the mechanical properties of TiAl-base alloys at high temperatures and the corresponding deformation behaviors are studied in this paper. Main factors during preparation that affect the mechanical properties of the final sintered alloy are discussed as well.