Abstract: Drop hammer impact test was used to study the failure mechanism and the compression after impact (CAI) of carbon fiber reinforced epoxy composite shaft tubes when subjected to different impact energy levels to simulate the low-velocity impact (LVI) process. ABQUAS finite element analysis technology and X-ray tomography (CT) techniques were used to investigate the internal failure mechanisms. Results show that, with the increase of impact energy, the deformation resistance of the composite tubes first increases and then decreases, and reaches a maximum value when the impact energy falls between 10 J and 20 J. The accuracy of the test results is confirmed by the fact that the energy absorption rates of the shaft tube with different energy levels differ little. CT results show that the composite shaft tube after LVI mainly fails in forms of delamination and resin cracking. Fiber fracture mainly occurs at the impact location, and the fiber fracture becomes more and more significant with the increase of impact energy. The finite element simulation results show that the fiber failure of composite shaft tube in the tensile direction is significantly less than the compression failure. The compression failure mainly diffuses along the fiber layout direction. The tensile failure mainly spreads along the axial direction and transverse direction, and the axial failure degree is greater than the transverse failure degree. The compression failure of the resin mainly diffuses from the impact position to the transverse along the axial direction. The diffusion shape is nearly round, the closer to the center, the failure is more obvious. The stretching failure range is a cross; the overall failure diffuses along the cross edge.