In order to improve the laser output quality of a dual-wavelength annular cavity laser, a saturable absorber of erbium-doped fiber was added to the 3 dB ring mirror to form a filter ring, and the filter ring and the output coupler were cascaded to realize the laser output filtering. Theoretical analysis and experimental verification were carried out. The results show that the laser output bandwidth of 1554 nm and 1562 nm wavelengths are 0.029 nm and 0.038 nm, the peak fluctuations of dual wavelengths are 0.0048 mW and 0.0087 mW, and the signal-to-noise ratio is 55 dB, respectively. The results show that the dual-wavelength laser based on the saturable absorber and 3 dB ring mirror filter structure has better linewidth narrowing characteristics and stability. It can be used in the field of high capacity communication and laser therapy.