Abstract: The continuous observation data of the PET gravimeter at the Hailar Earthquake Monitoring Central Station from 2021 to 2023 were taken as the research object. The original continuous gravity data were preprocessed using Tsoft software to obtain the residual gravity data. Time-frequency analysis of the residual gravity data was subsequently conducted using the HHT (Hilbert-Huang Transform) method, and the spectral characteristics of the background noise of the data were summarized. It was concluded that the background noise of the continuous gravity observation at the Hailar station was mainly concentrated in the frequency band of 0.05～0.28 Hz, with the dominant frequency at 0.23 Hz. This study aided in identifying the normal observation background and interference characteristics of gravity data, providing a background basis for analyzing seismic anomaly information.