All fiber picosecond ytterbium doped fiber laser with average output power of 39.2 W is constructed with a passively mode-locked seed laser based on semiconductor saturable absorber mirror and triple-stage master oscillator power amplifier (MOPA) configuration. When pumped power is 65.1 W,pulse width of output laser is 10.7 ps and repetition frequency is 68 MHz. This picoseconds fiber laser is used to pump a 4.5 m long photonic crystal fiber,and all-fiber supercontinuum laser source with average power 20.1 W is realized. The supercontinuum covers the whole spectral range from 600 to 1700 nm of the optical spectrum analyzer. The spectral flatness is 10 dB in the detected spectral range.