Self-ordered anodic TiO2 nanotubes (ATNTs) and related various nanostructures have received extensive attention in recent years. However, the relationship between porous morphology and anodizing current-time curve has not been quantitatively elucidated. Here, the simulation and separation of anodizing current-time curves are proposed to overcome this challenge. In this paper, ATNTs were anodized in the same electrolyte under a constant voltage at various temperatures. The interesting results show that the significant differences of nanotube length and surface morphology are mainly dependent upon the temperatures rather than the applied voltage. Simulation of the anodizing current-time curves obtained at various temperatures was performed through a theoretical formula. Then the total anodizing current was successfully separated into ionic current and electronic current. It is found that the ionic current and electronic current make different contributions to the growth of ATNTs. There is a linear correlation between nanotube length and ionic current, while the pore sizes and surface morphology are related to electronic current. The present results will provide a useful method to better understand the inherent formation mechanism of ATNTs. Furthermore, the nanotube length can be predicted by the simulation and separation of the current-time curve. (C) 2014 The Electrochemical Society. All rights reserved.