The actual load shedding verification test of large-scale “source-grid-load” friendly interactive system is introduced. A strategy validation technique based on preset instruction release mode is proposed. A time test method of actual load shedding control command transmission according to global GPS clock synchronization technology, and a frequency measurement method according to zero-crossing detection and digital filter technology are also proposed. The system’s control time and dynamic frequency can be accurately measured. Results show that quick load shedding time and frequency changes when DC blocking fault happens meet system requirements. The feasibility of the system function design is validated.