A high power all-fiber single-mode 1091 nm laser is constructed in master oscillator power amplifier (MOPA) configuration. The home-made seed source is an Yb3+-doped fiber ring laser with 22.5mW maximal output power. A two-stage pre-amplification configuration is employed to boost seed power to 3W. The ultimate output power of the main amplification stage is 62.5W, corresponding to an optical-to-optical conversion efficiency of 78.1%. No residual pump light or amplified spontaneous emission (ASE) is observed under maximal output power. Because of the using of fiber Brag grating (FBG) to select frequency in seed laser, the full width at half maximum (FWHM) linewidth of output light is narrower than 0.1 nm.