Abstract: Based on the Power Spectral Density (PSD) analysis method, the power spectral density characteristics of typical tilt observation data in Inner Mongolia, which on normal time or affected by gale, rainfall, barometric pressure and seismic wave is analyzed. The results show that: under the normal background, the daily PSD results are basically the same, and the second sampling data can obtain 8.3 mHz ~ 0.5 Hz high frequency information more than the minute sampling data; the gale interference affects frequency bands greater than 10⁻³ Hz, and causes significant increase in the energy of the second kind of ground pulsation noise signal to the second sampling data; the rainfall interference mainly affects the frequency band lower than 10⁻⁴ Hz, and also affects the 0.01 ~ 0.10 Hz frequency band of second sampling data; the barometric interference affects the 10⁻⁴ ~ 10⁻³ Hz and 0.01 ~ 0.10 Hz frequency band, and also may cause significant increase in the energy of the second kind of ground pulsation noise signal to the second sampling data; the frequency range and noise amplitude affected by seismic wave are directly proportional to the maximum amplitude and duration of seismic waves recorded by observation instruments. Moreover, in the affected frequency band, the background noise of the four kinds of interference signals is significantly higher than that in the quiet day.