The invention discloses a wide area self-adaptation spare power automatic switching method based on synchronous phasor measurement. By means of topology analysis, an association relationship between buses and lines is determined, a mode of operation of the lines and the buses is recognized, an initial operation state is recorded, faulty area, normal power supply area and area to be restored are determined, whether small power sources in a regional power grid are required to be immediately removed or not is determined, if the small power sources in the regional power grid are not required to be immediately removed, a spare power automatic switching power source is subjected to a quasi-synchronization grid connection, otherwise, all small power circuit switches in the area to be restored are tripped off, all non-fault working power source switches in a power-loss area are tripped off, and power restoration process is completed through circularly searching for power supply buses to be restored and closed corresponding line switches. According to the wide area self-adaptation spare power automatic switching method based on the synchronous phasor measurement, a centralized decision-making coordination mode which is specific to the integrated power grid is utilized so that a novel spare power automatic switching method has the advantages that the wide area is achieved, the method is capable of being self-adaptive to operation mode and the small power sources access to the power grid.