Geostationary BeiDou satellites monitor the total electron content (TEC) in the ionosphere over certain locations 24 hr per day without interruption and act as ionosphere‐based seismometers. The system detected perturbations in TEC before both the M6.1 Dali and M7.3 Qinghai earthquakes that occurred during the night of 21–22 May 2021. The TEC perturbations reside mainly over an area within a distance of ∼700 km from the epicenters of the earthquakes. The standing waves revealed the persistence of a subsurface wave source before the occurrences of the earthquakes, which differs from the co‐seismic ionospheric distributions propagating away from the epicenters. The resident waves in TEC and ground vibrations share a frequency of ∼0.004 Hz, which can be attributed to the resonant coupling between the lithosphere and ionosphere. Plain Language Summary Large earthquakes seriously threat human life and induce economic loss. However, predicting an earthquake remains as a huge challenge due to the lack of reliable precursor signals. Something must be happened before a large earthquake. Therefore, we are looking for the reliable geophysical parameters for identifying the precursor that human beings are desired. In this study, the ionospheric total electron content (TEC) from the geostationary satellites of the Beidou global navigation satellite system system recorded an unusual phenomenon of TEC perturbations resides in a particular area that appeared after mid‐May in the post‐sunset hours over China. The unusual phenomenon is significantly different from the morphologies of the traveling ionospheric disturbances and plasma bubbles over Asia in summer. The TEC perturbations reside over both two areas within a distance of ∼700 km where cover the epicenters of the M6.1 Dali and M7.3 Qinghai earthquakes occurred during the night of 21–22 May 2021. The perturbations in TEC and ground vibrations share a frequency of ∼0.004 Hz, which can be attributed to the resonant coupling between the lithosphere and ionosphere during the earthquakes. Key Points Ground vibrations and total electron content (TEC) perturbations share a frequency of ∼4 mHz Geostationary BeiDou satellites detected TEC wave prior to large earthquakes TEC perturbations resided persistently around the epicenters