Abstract: In order to solve the problem of dual wavelength laser stability and achieve the purpose of narrowing the line width, the unwanted oscillation modes was limited by adding ring filter into the laser structure. After simulation and calculation of filter, the dressing spectrum was obtained. Single frequency dual-wavelength laser with linewidth of 5.7kHz was obtained by experiments. After output power stability test, the power fluctuation within 1h was 0.6dB. The result shows that the effect of ring filter is very obvious.