The Experimental results of amplification of 1.531 μm femtosecond laser pulses using Er³⁺-doped fiber amplifier is reported. The femtosecond pulses generated by a self-starting additive pulses mode-locked Er³⁺ fiber laser with pulse duration of 410 fs injected into the Er³⁺-doped fiber amplifier (6 m, high doping concentration Er³⁺-doped fiber), the maximum amplification gain of 55(17.4 dB) and 64.4(18.1 dB) and the maximum single pulse energy (peak power) of 0.384 nJ(752 W) and 0.452 nJ(1295 W) have been obtained with forward and backward pumping respectively. The shortest output pulses duration are 501 fs and 309 fs with forward and backward pumping respectively.