In this study, an erbium-doped fiber femtosecond laser source based on divided-pulse amplification is introduced. Using a master-oscillator power-amplifier configuration, the seed pulse is first enhanced by a fiber preamplifier. Then, the preamplified pulse is divided into 64 replicas in sequence pulse dividers using polarization multiplexing. Finally, the seed pulse is simultaneously amplified and compressed in the main amplifier. A unique characteristic of divided-pulse amplification at 1.55 μm is that it can effectively reduce the nonlinearity-induced spectral distortion in the femtosecond pulse-amplification process for achieving pedestal-free pulse and finely control the nonlinear effect and managing the pump light intensity and fiber length in the spectrum-broadening process. In the pulse-amplification process, the pulse width could be compressed by the negative dispersion of fiber, thus, avoiding the use of grating or prism pairs. In the experiment, the low-nonlinearity and high-nonlinearity regions are investigated for the main amplifier. In the low-nonlinearity region, the amplified pulse achieves an average power of as high as 3 W with 830 fs pulse duration and 36.1 kW peak power. However, in the high-nonlinearity region, the amplified pulse achieves a pulse duration of as short as 137 fs with 1.54 W average power and 112 kW peak power. Furthermore, the contrast of 1560 nm femtosecond pulse is verified through optical frequency doubling in a periodically poled lithium niobate crystal. The optimized frequency doubling efficiency reaches up to 40.3%.