Abstract:   Contrast to the huge demand in measurement and testing, monitoring and communication, telecommunications and electricity and finance, a standard frequency source of high stability and high precision is crucial. GNSS disciplined crystal oscillator has combined the advantages of GNSS pulse per second signal which has good longterm stability. So GNSS disciplined crystal oscillator is widely applied for its high precision and low cost. In this paper, least squares algorithm, unbiased moving average filtering and Kalman filtering have been analyzed and compared.Those main filtering methods was applied to crystal oscillators which controlled in the same way.Their advantages and shortcomings have also been summed in this paper. Some meaningful suggestions are provided for the use of disciplined crystal oscillator in GNSS timing receiver.