Abstract: The optimized welding parameters for electron beam welding of 9 mm thick TC4 titanium alloy plate were obtained. A finite element model was established based on ABAQUS software, and the simulated results of the weld appearance and residual stress on the weld surface agreed well with the experimental results. This proved that the combined heat source with highly penetrating cone heat source and highly irradiative dual-ellipsoid heat source could characterize the electron beam welding. Further simulated results showed that high residual stress occurred around the weld, especially, dangerous three-dimensional tensile stress existed within the weldment.