Abstract: A kind of narrow line-width fiber laser using F-P fiber ring filter was proposed and experimentally demonstrated, which has a ring cavity. A F-P fiber ring filter consisted of two optical couplers of 30:70 and a length of 2 m unpumped Erbium-doped fiber. The comb spectrum produced by F-P fiber ring filter can magnify the free spectral range of the laser mode, eliminate mode hopping and increase the stability of the mode in a certain extent. The research shows that the fineness of F-P fiber filter can be improved through the optimization of Erbium-doped fiber and the selection of couplers. Unpumped Erbium-doped in the F-P fiber ring acts as saturated absorber, which can compress the linewidth of output laser effectively. Polarization-maintaining fiber grating(PM-FBG) and F-P fiber ring filter are both applied into Erbium-doped laser, the output of narrow linewidth and dual-wavelength laser is obtained, and the 3 dB linewidth of dual-wavelength laser are both less than 0.07 nm(spectrometer minimum resolution). The fiber laser had a stable output whose maximal peak power fluctuation was less than 0.4 dB within observation time of 2 h.