Abstract: TiO2 nano tubes (NT) were prepared by anodic oxidation in ethylene glycol and NH4F electrolyte. The phase structure and morphology of the TiO2 NT before and after annealed were analyzed by means of XRD and SEM. The results show that most of the prepared TiO2 NT were composed of amorphous state TiO2 phase which transformed into anatase and little rutile after annealed at 450 ℃ for 3 h and the grains grew well. The TiO2 NT with smooth wall had 200 nm in diameter and 30 nm in wall thickness, and the annealing didn’t destroy its shape.The formation of TiO2 NT experienced 3 steps including dense oxide layer formation, porous layer formation and formation and stable growth of the NT. The formation process was resulted from the joint effects of field induced oxidation, field induced dissolution and chemical dissolution, that approached a dynamic balance gradually.