Different TiOx thin films prepared by graded or sufficient oxidization of Ti are applied with Pt or Ag electrode in metal-insulator-metal(MIM)structures for studying the properties and mechanisms of resistive switching.The differences on the mobile oxygen vacancies in TiOx films and different work functions of the electrode films result in different insulator-metal interface states,which are displayed as ohmic-like or non-ohmic contact.Based on the interface states,the electrical models for MIM devices are analyzed and extracted.The electrode-limited effect and the bulk-limited effect can be unified to explain the mechanisms for resistive switching behavior as the dominant effect respectively in various conditions.All the current-voltage curves of the four kinds of specimens measured in the experiments can be explained and proved in accordance with the theory.