The invention discloses an adaptive wide-area damping controller and a control method thereof. The controller comprises an adaptive time-lag compensator, a phase shifting unit and a GrHDP unit; the adaptive time-lag compensator is used for performing adaptive time-lag compensation on a wide-area measurement signal to obtain a signal x(t); the phase shifting unit is used for performing amplifying and phase shifting on the signal x(t) to obtain a parallel phase shifting signal X(t); the GrHDP unit obtains a control signal u(t) matched with the current operating condition of an electric power system based on an adaptive dynamic planning according to the parallel phase shifting signal X(t); the control method comprises the steps of (1) performing adaptive time-lag compensation on the wide-areameasurement signal; (2) performing amplifying and phase shifting to obtain the parallel phase shifting signal; and (3) obtaining the control signal u(t) matched with the current operating condition of the electric power system through a GrHDP neural network. System low-frequency oscillation can be suppressed effectively in different operating conditions and different communication time lags, so that system transient stability is improved.