An all polarization-maintaining fiber laser system consisting of a low repetition rate mode-locked oscillator based on nonlinear amplified loop mirror cascaded with two-stage amplifiers are introduced. The experimental result shows that the output of the oscillating cavity is a stable mode-locked pulse with a maximum chirp, the pulse width is 90.25 ps, the corresponding Fourier transform limit is 141 fs, and it can be compressed to 431 fs with a center wavelength of 1064 nm and a 3 db spectral width of 10.4 nm. After the two-stage amplifier, the pulse average power can be amplified to 2.1 W, and the average output power is 1.5 W and the pulse width is 417 fs after compression using the grating pair. The whole system can obtain low repetition rate and high energy pulses output without passing through the acousto-optic modulator, which is a new idea to improve the pulse energy, and also facilitates the miniaturization of the mode-locked laser.