Using the phase mask method ,a fiber Bragg grating is fabricated in the circle shape inner cladding Yb 3+ doped double clad fiber(CDCF).By use of this grating as the output mirror of the CDCFL,the narrow linewidthlaseroperatingwavelength1055.2nmatthereflectcenterofthegratingispresented,FWHMis0.271nmand near 40 dB signal to noise ratio. There isn′t splice lose between CDCF and output mirror,and the bulk of CDCFL is reduced . Using a beam of uniform strength, which is fabricated by ourselves, bi direction chirp free tuning of center wavelengths of the fiber grating is realized, the tuning range up to 8.9 nm is obtained from 1051.1 nm to 1060.04 nm, the output laser 3 dB linewidths didn′t obviously change.