Unstable approach is a key issue in the safe flight operation of civil aviation industry. In recent years, the incidence of unstable approach events has increased. An important index to judge the unstable approach is the approach airspeed of the aircraft. CAAC and airlines actively develop monitoring procedures to monitor aircraft approaching airspeed overrun events. However, the accuracy of event monitoring is not high, and there are many false warnings. This paper studies the causes of false warnings, and designs an approach airspeed monitoring program based on the minimum ground speed function. This monitoring program can effectively reduce the occurrence of false warnings and significantly improve the monitoring accuracy of approach airspeed overrun events. Provide more reliable data support for analyzing aircraft unstable approach.