Ytterbium doped fiber lasers of special wavelength are investigated in theory and experiment. The gain competition between signal and amplified spontaneous emission is theoretically investigated based on the absorption and emission characteristics of Yb3+. Available approaches to suppress parasitic oscillation are analyzed. In experiments, 1018, 980, 1173 nm fiber lasers are established, and the maximum output power of the three fiber lasers are 309, 1.05, 15.7 W, respectively.