According to the wavelength characteristic of fiber coupler,its spectrum characteristics was analysed as a comb filter, and all-fiber comb-filter based on fiber couplers with different wavelength intervals were experimentally fabricated by splicing a section of single mode twin-core fiber (TCF) of different lengths between two single mode fibers (SMFs),and the extinction ratio is 25 dB. CO2 laser was used to trim the wavelength firstly,which results in the spectrum shifting to long wavelength and the change of extinction ratio.The trimming is based on the mechanism of residual stress and melting deformation between fiber and CO2 laser,and hydrogen-loaded TCF was used to improve the trimming efficiency.