Abstract: In order to realize 1120nm ytterbium-doped fiber laser with narrow linewidth, high power level, long wavelength (compared with 1030nm~1080nm), the resonator of fiber laser was composed of a normal single-mode Yb-doped fiber and a pair of fiber Bragg gratings (FBG). The theoretical-optimized active fiber length is used to ensure that pump light is entirely absorbed and nonlinear effect is suppressed. After theoretical analysis and experimental verification, the results show that when laser threshold pump power is 40mW and the launched pump power is 265mW, laser output signal power is up to 35mW with optical-to-optical conversion efficiency of 13.2%, central wavelength of 1120.9nm, output light linewidth of 0.03nm. The performances of the laser contribute to high reflectivity output coupler FBG, short cavity and low power operation. The laser can be injected into fiber amplifiers.