A saturable dual wavelength laser based on a saturable absorption ring filter is designed.An unpumped erbium doped fiber is inserted into a 3 dB ring mirror to form a saturable absorption ring mirror filter,which is inserted into a ring laser to achieve a stable dual wavelength output by adjusting the polarization controller.After calculation,6.4 m erbium doped fiber is selected as the gain medium,and a section of 2 m unpumped EDF is used to form a saturable absorption loop mirror filter in combination with a 2×2 3 dB coupler to suppress the supermode.In order to suppress the mode competition caused by the uniform widening of erbium doped fiber at room temperature,1554 nm fiber Bragg grating(FBG)and 1562 nm FBG are selected for dual wavelength lasing.Simulation is conducted on the Optisystem platform and experiments are set up to test the output laser power,signal to noise ratio,stability,etc.The output signal is observed and analyzed with a Optical Spectrum Analyzer.In the experiment,the stable output of dual wavelength laser at room temperature is obtained,and the signal to noise ratio of the two wavelengths is 54.70 dB and 57.50 dB respectively.The 3 dB bandwidth is about 0.13 nm.