The practical low measurement precision open-loop FOG uses polarization-maintaining technology, modulated by sine signal added to a PZT. The harmonic components analysis method, Chebyshev filter, self-adapting sample frequency adjustment, FFT and digital correlation are used to process the gyroscope's signal, and finally reach 2 deg/h measurement precision. In this paper, the method to choose and stabilize the action spot of the gyroscope and the method to improve the precision of the gyroscope are mentioned.