The invention provides a method for coordinating and optimizing small-interference and large-disturbance damping of an alternating-current and direct-current sending-tend unit. The method includes steps of (1), constructing a stability analysis model for an alternating-current and direct-current hybrid sending-end power grid; (2), quantitatively evaluating small-interference and large-disturbance oscillation damping characteristics of the hybrid power grid; (3), determining an adjustable range of PSS (power system stabilizer) parameters; (4), analyzing a suppression effect of the PSS parameters to large-disturbance oscillation; and (5), selecting the type of a PSS coordinated with the small-interference and large-disturbance oscillation damping and optimizing the parameters coordinated with the small-interference and large-disturbance oscillation damping. The adjustable range of the PSS parameters meets requirements of small-interference oscillation damping. The method for coordinating and optimizing the small-interference and large-disturbance oscillation damping of the alternating-current and direct-current hybrid sending-end unit by the aid of the PSS has the advantages that the failure impact resistance of a direct-current sending-end system can be improved, and the safe and stable running level of the power grid is improved.