Abstract: A hundred nano-joules femtosecond (fs) laser amplification system based on the polarizationmaintaining Yb3+ fibers was proposed in this paper. In the proposed system, a Yb-doped mode-locked laser oscillator was used as the light source. Using the chirped pulse amplification method, a two-stage polarizationmaintaining Yb-doped fiber amplifier was adopted. Experimental results show that, with compression of the output light, the output pulse energy can reach 113 nJ and the pulse duration is measured as 221 fs.