A new-style, all-fiber, broad-band tunable erbium-doped fiber ring laser is proposed. The wavelength continuous tuning is realized by using a single-mode/multimode/single-mode fiber as a filter, in which the multimode fiber is wrapped around a polarization controller, and is spliced to a single-mode fiber at each ends. By carefully adjusting the polarization controllers in the cavity, the output central wavelength of tunable single-wavelength laser is tunable from 1542 to 1560 nm over a range of 18 nm, with a signal-to-noise ratio of 40 dB and the 3-dB linewidth of 0.096 nm. Furthermore, by appropriately rotating the polarization controllers and changing the pump power, wavelength continuously tunable dual- and triple-wavelength laser output is also experimentally demonstrated, and the wavelength selection and switching can be achieved by adjusting the polarization controllers in the cavity.