In this paper, based on the Brune model, the apparent stress and other focal source parameters of ML≥3.0 earthquakes in northern Qinghai Province from January 2010 to May 2020 were calculated by using the waveform data recorded by Qinghai digital seismic network. The spatial-temporal variation characteristics of apparent stress were studied. The relationship between apparent stress anomalies and moderate strong earthquakes was discussed based on M≥5.0 earthquakes occurred in northern Qinghai Province, and the prediction efficiency was tested. The results showed that high value of apparent stress occurred prior to most of M≥5.0 earthquakes, indicating that obvious anomaly of high apparent stress in northern Qinghai Province has certain indication significance for moderate strong earthquakes.