The present invention provides a device for synchronous measurement and analysis of the electric system full frequency spectrum oscillation phasor based on three-phase total instantaneous power. The method comprises: a three-phase total instantaneous active power is measured at a power grid branch measurement point through the measurement of the three-phase instantaneous voltage and the instantaneous current waveform record, and a time synchronizer is employed to obtain high-precision markers for each measurement point; the frequency-division section processing technology is employed to obtain the parameters of an oscillation mode included by each frequency range aiming at the special parameters employed by each frequency range such as filtering parameters, the downsampling rate parameters, calculation data windows and calculation steps; and the initial phases of the whole calibration times (10 seconds, the whole second, the 0.1 second and the like) are taken as the phase angles of the oscillation phasor so as to realize the expression of the wide area analysis oscillation phasor. In order to further improve the precision of the phasor calculation, the selection of the whole calibration times avoids the boundary points of the time windows; and moreover, the detected frequency, amplitude, initial phase, damping coefficient and markers of the power oscillation satisfying the threshold of each frequency range are outputted in real time.