Conventional damping controllers cannot adapt effectively to the changes of network structures and operating conditions， therefore， the low-frequency oscillation still occurs frequently. In this paper， a self-searching adaptive damping controller is designed based on wide area dynamic signals. Parameters of the controller are tuned according to the damping ratios of the weakly damped inter-area oscillation modes estimated on line by an improved Prony algorithm. In this approach， the model identification is not included， since it is difficult to guarantee its accuracy in real power systems. The proposed adaptive strategy is verified by numerical simulations of China southern power grid. Furthermore， the adaptive controller is implemented by hardware and tested on the platform of RTDS and WAMS. The close-loop experimental results are also presented to show the effectiveness of adaptive HVDC damping controller and the feasibility of wide-area damping control.