Abstract: Preparation of complex thin-walled titanium alloy structure can be well solved by hot isostatic pressing technology, however, which is not suitable for the large structure products because of the cost and equipment capacity. An ideal choice of preparation of large structure is electron beam welding (EBW) according to its characteristics. 5 mm thick plates of hot isostatic pressing TC4 titanium alloy were welded by EBW, and the microstructure and properties of the welded joint were studied. The distributions of microstructures in weld zone and heat affected zone were observed, and the mechanical properties of welded joints was tested and analyzed. According to the analysis results of the hot isostatic pressing TC4 titanium alloy, aʹ martensite phase formed in weld zone and heat affected zone of EBW joint, which can strengthen the weld zone and heat affected zone, and lead to the hardness and strength of welded joints are higher than that of the parent material.