The safe and stable operation of power system is threatened seriously by poor damping low-frequency oscillation in interconnected system. Aiming at the flexible operating conditions and insufficient damping in the large-scale renewables penetrated system, a data-driven global sensitivity calculation method is proposed in this paper, based on which, the correlation between the electromechanical interarea mode and the active power of the generator is quantitatively analyzed. Then, the optimal allocation scheme of the number of modulation units and the corresponding modulation amount is given. Finally, an active power modulation strategy of generator based on the proposed global sensitivity is constructed to improve the damping of interarea mode. The simulation results of IEEE 16-generator 5-area system show that the proposed global sensitivity calculation method can select the generator participated in modulation accurately, and the proposed damping modulation strategy can improve the system damping effectively.