Abstract: Using the Welch algorithm, the different time periods’ earthquake-free records of the continuous three-component seismometer waveform of 28 seismic stations in Beijing Seismic Network were selected, the power spectrum density of the base-based noise was calculated and statistically analyzed. The results show that the dominant frequency of each base noise background of Beijing Seismic Network has its own characteristics, and the difference between the high and low frequency noise power spectrum curves is large. In the 1~20 Hz frequency band, the high value area of the background noise value in Beijing appears near the central city, and the low value area appears in Liulimiao and Miyun in the north, and Shangfangshan in the south, which is mainly affected by man-made noise. In the frequency range of 0.008~0.1 Hz, there is little difference in all areas of Beijing.