In a fiber amplifier which is based on master oscillator power amplifier structure, generating a seed source with narrow linewidth and stable temporal property is very important for suppressing nonlinear effects and obtaining multi-kilowatts power. The random fiber laser based on Rayleigh scattering and Raman gain has been widely investigated due to the superior performance on temporal stability. Taking 1018 nm fiber laser based on self-fabricated fiber grating as the pump source, a 10.6 GHz, 1067.6 nm random fiber laser as the seed source is achieved by adopting a half open cavity. A three-stage power amplifier structure boosts the seed to 42.8 W, the linewidth is maintained during the power scaling process, which shows that the light source has a great potential to be used as the seed source of multi-kilowatts fiber amplifier.