Ag/SiO2/Pt memristors are fabricated to investigate their resistive switching characteristics. The devices exhibit stable and reversible nonvolatile bipolar resistive switching behavior under DC voltage sweeps with a current compliance (CC) of 1 mA. Moreover, electroforming process is not required in the first I–V cycle, the values of VSET and VRESET are 0.2 V and −0.2 V, respectively. Meanwhile, volatile resistive switching behavior of Ag/SiO2/Pt devices is also obtained under lower CC. The mechanism of two resistive switching behaviors in Ag/SiO2/Pt memristors are analyzed.