A finite element (FE) model for the numerical control (NC) bending of Ti-3Al-2.5V titanium alloy seamless tube is established,considering the variation in the contractile strain ratio (CSR) and elastic modulus (E).The wall thinning characteristics of Ti-3Al-2.5V tube under different geometric and process conditions were investigated.The results showed that the CSR-E variation can change the wall thickness,but has no remarkable effect on the change characteristics.The reasonable parameter ranges are as follows:a bending-radius range not less than 1.5 times the outer diameter,a bend angle up to 180°,and a mandrel extension of 0-3 mm.The friction coefficient between the pressure die and the tube should be in the range of 0.20-0.35,and between the bending die and the tube should be in the range of 0.05-0.15.As long as the performance meets the requirements,the relative push-assistant speed should be as small as possible.