Single frequency fiber laser is the most promising optical source in fibre optic communication, which plays an important role in fibre optic sensor, laser radar and laser range finde. Generally, the performance of the single frequency fiber laser was evaluated by the phase noise. The oscilloscope and dynamic signal analyzer method were adopted to design phase noise of single frequency fiber laser. Using power spectrum and the integral sources of different pump power, seed source power and wavelength of the fiber laser phase noise were analyzed qualitatively, the results show that, the greater pump power can get the low frequency phase noise. For the different seed source powers, phase noise is in the proportion of basic test frequency at the same level. For testing seeds of different wavelengths which is different proportions of high frequency phase noise, the biggest percentage of seed wavelength is 1 560.48 nm.