A synergic identification method for dynamic stability of a power system is provided, including: acquiring each dominant oscillation mode; acquiring a critical wavelet scale factor range corresponding to each dominant oscillation mode; calculating an oscillation modality of the dominant oscillation mode corresponding to the critical wavelet scale factor range by a right singular vector corresponding to a maximum value among first singular values of each reconstructed wavelet coefficient matrix in the critical wavelet scale factor range; calculating, according to the relation between left and right feature vectors and the estimated oscillation modality, a left feature vector corresponding to each dominant oscillation mode and calculating a participation factor of each measurement channel in this dominant oscillation mode; calculating direction cosines between measurement channels by the oscillation modality of the dominant oscillation mode, and classifying coherent generator groups or coherent bus groups in the system by the direction cosines.