The invention discloses a system and a method for phasing a power supply of a high-voltage busbar of a power station. The system comprises a working power supply unit, a generator circuit breaker unit, a working power supply common-box busbar, a working power supply incoming soft joint, a working power supply incoming switch, a working power supply incoming voltage transformer, a backup power supply unit, a backup power supply common-box busbar, a backup power supply incoming soft joint, a backup power supply incoming switch, a backup power supply incoming voltage transformer, a high-voltage busbar voltage transformer and a high-voltage busbar. By adopting the system and the method disclosed by the invention, the phasing for the power supply of the high-voltage busbar can be implemented, and the safety and reliability are relatively high.