An acoustic optical modulator (AOM) laser power feedback loop was used to suppress the intensity noise of the pump laser, and the intensity noise reduction of more than 5 dB (@f=1 Hz-50 kHz) was obtained. The relative intensity noise of the 2 μm single-frequency fiber laser obtained 3-15 dB suppression (@f=1 Hz-50 kHz), and the intensity noise level was close to the detector limit (@f=40-400 Hz). Meanwhile, its frequency noise is also suppressed by 3-8.4 dB. After the two-stage Thulium-doped polarization-preserving fiber amplifier, the output power of the 2 μm single-frequency laser was increased to about 5.2 W with almost no significant increase in frequency noise, and the frequency noise levels were all at 100 Hz/ $\sqrt {{\rm{Hz}}} $ (f>13 Hz). The frequency response was 45 MHz/V, the frequency drift was 41.4 MHz@1 h, the power fluctuation was less than 0.4%@1 h, and the linewidth was less than 5 kHz. This kind of ultra-low noise 2 μm single-frequency fiber laser will be a candidate laser source for the next generation of gravitational wave detectors.