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The effects of process parameters and characteristics such as relative extrusion amount, final reaming value and sleeve split placement on the fatigue gain of the split sleeve cold expansion TA15 titanium alloy hole structure were studied by the comparative fatigue test method. The results show that the split sleeve cold expansion technology can effectively improve the fatigue strength of the hole structure of TA15 alloy and prolong its fatigue life. The larger the relative extrusion amount, the greater the fatigue gain of the hole cold expansion, but the TA15 alloy is very sensitive to the extrusion amount, small relative fluctuations in the amount of extrusion can cause significant fatigue gain fluctuations. Under the premise of completely removing the material ridges left by the sleeve split in the hole wall, the 0.190 mm and 0.065 mm reaming amount are pressed influence the cold expansion fatigue gain significantly, the fatigue gain is greater at 0.190 mm single-sided reaming. Under the maximum fatigue load of 400 MPa, the placement of sleeve split has a significant impact on fatigue life, the sleeve split needs to be placed away from dangerous sections in actual split sleeve cold expansion operations.