Abstract:We use the frequency spectrum method to process the observation data of multiple seismographs in Sichuan and analyze the spectrum characteristics of the data before the 2008 Wenchuan earthquake. The results show that obvious abnormal disturbances occurred 3 to 4 days before the earthquake. The dominant frequency ranges of abnormal signals are 0.18 to 0.25 Hz and 0.1 to 0.18 Hz. The signals in the frequency band of 0.18 to 0.25 Hz are mainly affected by the western Pacific typhoon. The signal anomaly started on May 9th, reached its maximum intensity on the 11th, and then began to attenuate; while the signal in the 0.10-0.18 Hz frequency band gradually increased from May 9th, increased sharply 10 hours before the earthquake, and reached the strongest before the earthquake. Signals in the frequency range of 0.10 to 0.18 Hz change sharply before the earthquake. The analysis results of all stations are similar, which may be related to the incubation of the earthquake.