A fiber chirped pulse amplification system based on Yb3 + doped fibers is demonstrated. The seeder is a mode-locked fiber laser with semiconductor saturable absorber, the chirped pulse amplification technique is applied to stretch the 1030 nm pulse to several hundred picoseconds to be amplified. The single mode picosecond pulses with average power of 50 W and repetition rates of 211 kHz are achieved by using multistage pre-amplifier consisted with Yb3+ doped single mode fiber amplifier and double cladding fiber amplifier and the main amplifier with a large mode area rod-typed photonic crystal fiber as the laser gain material. Properly controlled the gain and the nonlinearity in every step of the amplification system, the influence of nonlinear effects are effectively suppressed on the pulse of time domain in high energy amplification. Laser pulses with pulse duration of 887 fs are generated by a reflective grating-pair compressor, corresponding to single pulse energy of 124 μJ and peak power of 139.8 MW. This experimental result of hundred micro joules level femtosecond laser based on fiber structure is firstly reported in China.