Effect of the deformed microstructure on mechanical properties of an orthorhombic (Ti2AlNb) based alloy of Ti-22Al-25Nb (mole fraction, %) has been investigated. It was found that the deformed microstructures in different portions of a free forged rod with diameter of 30 mm were quite different and thus resulted in the different mechanical properties after the same subsequent heat-treatment. One deformed microstructure with less primary α2/O particles and a larger and equiaxed B2 grains resulted in poor RT ductility, but the other one with a relatively larger amount of the primary α2/O particles and non-equiaxed B2 grains had good combination of the tensile strength and ductility both at RT and 650 ℃. It was also found that two different deformed microstructures were obtained for the hot rolling plates with thickness of 3 mm even processed under an identical nominal rolling and the same post-deforming heat treatment conditions. One only has 3.5% of RT tensile elongation and the other up to 8%.