A tunable erbium-doped fiber (EDF) laser based on parallel single mode fiber (S MF)-multi-mode fiber (MMF)-SMF (SMS) structure is proposed.Two parallel SMS structures are used as filters in the ring cavity of the laser.By controlling th e loss of the cavity,the laser is switchable between the single wavelength mode and the dual-wavelength mode.The side mode suppression ratios (SMSRs) are more than 35dB in two modes.The wavelength of the laser is tuned by the bending.When the laser op-erates on the single wavelength mode,the center wavelength of the laser shift s from 1558.3 nm to 1557.3nm with the displacement increasing from 0μm to 60μm controlled by the micrometer.Th e experiment shows that proposed laser not only has the advantages of simple structure and low cost,but also has the switchable and tunable characteristics,which means that the laser is promising in wavelength division m ultiplex (WDM) optical communication systems,optical fiber sensing, high accuracy spectral measurement and many other fields.