The welding residual stresses were investigated with both experimental and numerical simulation methods,and the mechanism of the reheat cracking in Ti2AlNb EBW joint was also discussed with inspections on the characteristics of the cracks and the microstructures evolution during the heat treatments. The results showed that the EBW weld center suffered tensile stresses in three directions. The longitudinal tensile stress was the dominating tensile stress, which is more than 1100MPa, the tensile stresses in tansverse and thick directions had small values, except the plate is thick plate. Compared with the straight welds, the circular welds had lower hoop tensile stress, while higher radial tensile stress, especially in the small diameter circular weld. The formation of the reheat cracks was responsible to the precipitation layer at the grain boundary and the higher tensile residual stresses. The cracks were created and propagated along the interface between the precipitation layer and the matrix. The precipitation appeared when heating up to about 700°C with the heating rate below a critical value.