Simulation and experimental results for high repetition rate all-normal dispersion Yb:fiber ring lasers are demonstrated for the cavity dispersion from 0.01 to 0.025 ps2. The simulation shows that the pulse spectrum has the potential to reach > 30 nm for the dispersion of 0.014 ps2 under practical pump power. This potential is proved by the experiment. Maximum spectral width of 30 nm is achieved at the repetition rate of 285 MHz under the 850-mW pump power. Average output power is 550 mW and dechirped pulse is 78 fs.