For inter-area low-frequency oscillation in power systems，a novel design strategy for damping controller with wide-area measurements is proposed. This strategy adopts the quasi real-time data provided by wide-area measurement system（WAMS） to establish time-delay model of power system by employing Prony identification of transfer function and Pade approximation of dead time delay. Then the damping controller is designed based on the mixed-sensitivity H ∞control theory and pole placement approach to ensure the H ∞performance index and suitable pole placement of closed-loop system to achieve the required dynamic performances. Simulation results of 2-area 4-machine power system and New England test power system show that the damping controllers with wide-area measurements feedback can significantly increase the damping ratios of inter-area low-frequency oscillation， and are insensitive to time-delay.