Radio-frequency magnetron sputtering has been used to deposit Ni-rich nickel oxide nano-films to form a metal-insulator-metal structure, which exhibits resistive switching behavior. Memory characteristics of the structure have been investigated. The ratio of the current of the structure at the reading voltage of 0.05 V between a low-resistance state (LRS) and a high-resistance state (HRS) was observed to be >103, showing a large memory window at a very low reading voltage. The memory window was well maintained within the time limit of the experiment (5 × 104 s), exhibiting good memory retention. The current transport at both the LRS and HRS has been studied, and the result suggests that the formation and annihilation of a conductive filament are responsible for the resistive switching.