The frequency of power system forced oscillation (FO) is near to the power system inter-area oscillation modal,so it can lead to severe resonances. This paper firstly proposes a novel forced oscillation modal detection method, which aims to obtain the analytic solution of the system force oscillation modes subjected to forced disturbance with small signal analysis; subsequently,this paper develops a power oscillation damping (POD) control approach to mitigate the FO and inter-area oscillation without installing additional PODs. The modified 14-machine power system is developed to verify the robustness and superiority of the proposed method.Simulation examples show that the proposed method is robust to external disturbances and has obvious advantages compared with traditional methods.