We report resistive switching in single Ag2S nanowires contacted with two silver electrodes. The resistance evolution over time was studied by persistently applying a fixed 0.1 V bias at 10 K, and it is found that the device alternated at the ON and OFF states. The resistive switching behaviors are ascribed to the formation and rupture of metallic Ag filament inside the Ag2S nanowire. The wait time for such switching was significantly longer than those previously reported (a few seconds for the initial switching on, by Liang etal, [Small 1, 971 (2005)]), which was discussed by considering the local Joule heat and charge accumulation during the wait time. The devices may have potential applications on nonvolatile memory.