TiO2 nanotube array thin films, which have great potential in many fields, such as solar cell [1], photo catalyst [2], photo-induced cathodic protection for metals [3] and bioactivity [4], have been attracted lots of interest since they were discovered.In order to investigate the formation process of the TiO2 nanotube array thin films, the EIS spectrum and current density were measured during the anodic oxidation.The results showed that the formation process could be divided into three stages.