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The welding of 15mm TC18 titanium alloy thick plate is realized by electron beam welding. The effect of different welding speeds (10 mm / s, 20 mm / s, 30mm / s) on the fatigue properties of the electron beam welded joints for TC18 titanium alloy was investigated. The macroscopic morphology, microstructure and fracture characteristics of the joints were analyzed by optical microscope, scanning electron microscopy and transmission electron microscopy, and the fatigue properties of welded joints were studied and tested by an electronic universal testing machine. The results showed that the weld fusion zone was mainly composed of columnar β phase and acicular α martensite phase. The upper melting width, the middle melting width and the lower melting width were obviously reduced, and the grain size gradually decreased with the increased of welding speed, which resulted in the increase of fatigue properties of welded joints. At Nf =107, the fatigue limit of the weld was increased by nearly 29% with the welding speed from 10mm/s to 30mm/s. The fatigue fracture of the joints can be divided into three typical regions of fatigue crack source zone, expansion zone and instantaneous zone, and the fatigue cracks all originated from the surface of the specimen. With the increased of welding speed, the proportion of instantaneous area decreased and the fatigue performance increased.