  This paper reports the achievement of 120W single-frequency narrow linewidth
1018nm laser based on wide-tunable DBR fiber seed source. The DBR structure
seed source uses 8mm long doped optical fibers with a line width of 3.25k. The
wavelength tuning range of this seed source exceeds 1.5 nm with the temperature
range from 1{\deg}C to 95{\deg}C. The tuning wavelength and temperature show
extremely high linearity, and there is no mode hopping during the tuning
process. By adopting a multi-level fiber amplification structure, selecting
appropriate doped fibers and optimizing their length, an output power exceeding
120W of 1018nm laser has been achieved. Measurement results indicate that the
slope efficiency of the main amplification 77.3%, with an amplified spontaneous
emission (ASE) suppression ratio greater than 60 dB. he output linewidth is
10.3 kHz, and the beam quality factor M2 is less than 1.3.
