In order to solve the problem of folding defects that are prone to occur during the direct upsetting process of tube end flange, for TA2 pure titanium tube, a new method of flaring-upsetting combined forming for tube end flange was proposed, and the pure titanium thin-walled tube end flange was successfully prepared. Then, the influence laws of flaring pre-deformation at different angles on the formation position and size of folding defects during the upsetting process of tube end flange were studied by experiment and numerical simulation methods, and the radial velocity distribution under the upsetting stroke of 50% for the tube end flanges with flaring angles of 20° and 0° was analyzed and compared. The results show that the strain of folding region is large in numerical simulation, which is caused by the folding defect formed by the extrusion of tube walls. The flaring pre-deformation causes the internal bending moment to occur when the free tube end flange is upsetting, which changes the metal flow behavior of pure titanium. The depth of folding defect decreases with the increasing of flaring angle. Compared with the direct upsetting, the folding defects of tube end flange formed by flaring 20° first and then upsetting are transferred from the inner wall to the upper surface, and the depth of folding defects is relatively small, which does not affect the overall quality of tube end flange after the removal of machining.