Annealing treatments in the temperature range of 800℃ to 900℃ was applied to the electron beam weldments of powder metallurgy Ti2AlNb alloys to investigate its influence on microstructure and tensile properties at room temperature and 650℃. The results show that there are coarse columnar and equiaxed B2 grains in the fusion zone (FZ) in the as-welded weldments. Transformation from B2 phase to O+B2 phase occurs in the FZ during the post-weld annealing treatments. The morphology of the O phase is characterized as the basket-weave structure and the size of the O phase plate increases with the increase of the annealing temperature. The microhardness in the FZ of the as-welded weldments are higher than that in the base metal (BM). After the annealing treatments, the microhardness in the FZ increases significantly, which gradually decreases with the increase of annealing temperature. At room temperature, all tensile speciems are fractured in the FZ. The tensile strength of the as-welded weldments is close to that of the BM and local large plastic deformation occurs in the FZ. However, the strength and ductility of the weldments decrease slightly after the post-weld annealing treatment. At 650℃, most of the tensile speciems are fractured in the FZ. The as-welded weldments are failured in the FZ, which are characterized as brittle intergranular fracture. After the annealing treatments, there is an apparent improvment of strength and ductility in the FZ of the weldments. With the annealing temperature increasing up to 900 ℃, the failured locations are shifted from the FZ to the BM.