A new kind of single-longitudinal-mode and wavelength-switchable fiber laser is proposed and experimentally demonstrated. Such a fiber laser has a ring resonant cavity. An unpumped erbium-doped fiber (EDF) in the cavity is used as the saturable absorber to achieve single-longitudinal-mode operation. An 1×2 optical switch and 2 parallel fiber Bragg gratings (FBGs) are used as the wavelength selection module to achieve wavelength-switchable operation. At 17.5-dBm output power of EDF amplifer, the single-longitudinal-mode laser with 2.5-dBm power and 3-kHz linewidth is generated. The wavelength is randomly switched between 1545.2 nm and 1556.4 nm by applying the suitable electrical signal to optical switch.