It is difficult to extract its anomaly information because the disturbed data is very complex in the earthquake precursory observation. In this paper, it analyses frequency spectrum characteristics of disturbed data about the high frequency interference，periodic disturbance of water level and wind，co-seismic strain of perpendicular pendulum tiltmeter，FFT and HHT marginal spectrum in Heilongjiang Province. The dominating vibration frequency is at over 1.7×10－3Hz in a period of lower than 10min. The three kinds of method have obvious differences. The power spectrum and FFT are effective methods in extracting noise and disturbed data. HHT marginal spectrum is an effective method in extracting coseismic strain. This study will enrich the theoretical application of spectrum analysis in extracting disturbed data.