The invention discloses a subsynchronous oscillation inhibition method based on a UPFC (unified power flow controller). An additional control signal is superposed in a reference signal of a parallel-side controller or/and a series-side controller of the UPFC in order that subsynchronous frequency damping torque is generated. A method for acquiring the additional control signal comprises steps of: extracting the component signals of a generator rotating speed deviation signal in various torsional oscillation modes and successively performing amplification phase shift, amplitude limiting, and superposition on the component signals; amplification phase shift and amplitude limiting parameters are predetermined through optimization solution by using a maximum sum of the electrical damping and mechanical damping of a generator in various torsional oscillation frequencies as an optimization objective. The invention also discloses a subsynchronous oscillation inhibition device based on the UPFC and a power generating system. The subsynchronous oscillation inhibition method and device may effectively inhibit subsynchronous oscillation and are easy to implement.