Abstract: NiO x films on Pt‐covered Si (100) substrates are deposited by means of radio frequency magne‐tron sputtering ,and the effects of oxygen partial pressure on their microstructures and resistive switching properties are investigated .Microstructure investigation reveals that NiO x films deposited with 20%‐oxy‐gen partial pressure exhibit a polycrystalline structure with a preferred crystalline orientation direction of [200] and a smooth surface topography .Columnar crystalline grains with an average diameter of 13.8 nm are perpendicular to the substrate .With the increase of oxygen partial pressure ,the saturation magnetic moment of NiO x films decreases sharply .Compared with those samples deposited with other oxygen par‐tial pressures ,the NiO x films deposited with 20%‐oxygen partial pressure show the best bipolar resistance switching characteristics:the average ratio of high/low resistance is more than 10 at the read voltage of-0.6 V .The logarithmic plots and power‐law fittings for current‐voltage curves demonstrate that an ohm‐ic conduction process is dominated on the low resistance state ,while on the high resistance state ,an ohmic conduction process is still worked when the applied gate voltage is lower than 0.4 V ,and a trap‐controlled space‐charge limited current conduction process is dominated when the applied gate voltage is higher than 0.4 V .