A high repetition rate and wide spectrum picosecond pulsed all-fiber Yb-doped laser is experimentally studied. The laser with all-fiber structure uses the master oscillator power amplifier technology. The broadening of the spectrum is caused by the nonlinear effect. Passively mode-locked technique of oscillator is realized by semiconductor saturable absorber mirror. The laser operates at 1031.3 nm with 3 dB spectral width of 1.51 nm. Its pulse width is 3.1 ps and the repetition frequency is 21.3269 MHz. An acoustic-optic modulator is applied to reduce the repetition rate to 2.1 MHz. The down-converted signal light passes through a three-stage Yb-doped fiber amplifier, and the main power amplification is realized in 30 μm/250 μm large mode field double-clad Yb-doped fiber. In the end, the pulse laser output is obtained with average output power of 20 W, pulse width of 20.8 ps, spectrum range from 640~1700 nm, single pulse energy of 9.5 μJ, and corresponding peak power of 0.46 MW.