The wide-area measurement system (WAMS) provides the synchronized dynamic measurement for power systems; however, the effective monitoring of subsynchronous oscillations (SSO) with WAMS has not been achieved. To achieve SSO monitoring based on the synchrophasors provided by WAMS, a synchrophasors-based SSO identification technique was proposed in this paper. On the basis of existed synchrophasors, this technique can obtain the frequencies and amplitudes of both the fundamental and subsynchronous components of currents and voltages in SSOs effectively. In this technique, the impacts of both the fast Fourier transform synchrophasor algorithm and the sampling rate of synchrophasors on the spectrum of the subsynchronous component were taken into account. On one hand, the SSO frequency was obtained according to the spectrum of magnitudes of synchrophasors. On the other hand, a correction method for the spectrum of magnitudes of synchrophasors, in contrast to a constructed standard waveform that proportionally matches with the measured SSO, was applied to obtain the actual amplitudes of both the fundamental and subsynchronous components. Both the numerical simulation and the illustrations of two different actual SSO incidents were presented with comparisons to verify the correctness and feasibility of the proposed technique. This technique is of important practical value for mitigations of SSO in actual power systems.