Based on the China Southern Power Grid system, the propagation characteristics of electromechanical disturbance in the actual large power grid are studied. The time-space distribution characteristics of power system frequency are analyzed, and the estimation method of the disturbance propagation velocity is given. The PSD-BPA electromechanical transient simulation program is used to simulate the frequency response characteristics of power system when the generator tripping occurs at different locations, and the time and speed of the disturbance propagation to each observation point are estimated. The propagation characteristics of the disturbance in the actual large power grid are obtained through comparative analysis. Aiming at the pure DC connected asynchronous interconnected power grid, the frequency response characteristics of power grid and the influence of the receiving-end power grid disturbance on the sending-end power grid are studied, and the mechanism of DC system transmission disturbance is discussed. Finally, the conclusions drawn from the work of this paper are summarized, which will provide reference for the study of wide-area stability control of interconnected large power grids based on electromechanical wave theory.