Abstract: A 476 W 1018 nm ytterbium fiber laser has been demonstrated employing large mode area fiber. A high power ytterbium doped fiber amplifier pumped by 6 high brightness 1018 nm fiber lasers is constructed. The maximum output power is 2140 W, with a slope efficiency as high as 86.9%. The beam quality M2 factor is measured to be 1.9. Further power scaling is very probable if more powerful pump sources are provided.