In order to realize a dual-wavelength laser output,a ring cavtiy erbium-doped fiber laser based on fiber ring filter was proposed.In designed system configuration,one polarization maintaining-fiber Bragg grating was adopted as wavelength selector.The fiber ring filter was frabricated by two couplers with 20:80 splitting ratio and 2 m polarization maintaining fiber to constrain the mode hopping and improve the working stability,and the polarization controller inserted into the filter can be used to switch laser wavelengths.In order to guarantee the system stability,a saturable absorber of 1 m long was spliced between circulator and polarization maintaining-fiber Bragg grating.In the expriment,the working threshold is 71 mW,and the spectrum character of two lasres are improved after filter is used.The switchable single wavelength and two simultaneous wavelengths can be realized by adjusting the polarization controller,the wavelength space is 0.88 nm,and the maximum output power of single laser 1 535.5 nm and 1 534.7 nm is 0.078 dBm and -2.585 dBm,and 3 dB linewidth are 0.16 nm and 0.15 nm respectively.At room temperature,over 20 min scan time,the wavelength shifts are less than 0.06 nm ,the power fluctuation are less than 1.3 dB.