Embodiments of this application disclose a signal transmission method and a related device thereof. The method in this application includes: obtaining N parameters of a target cell, where the parameters indicate a real-time status of the target cell, and N is an integer greater than or equal to 1; and shutting down at least one first orthogonal frequency division multiplexing (OFDM) symbol in a first subframe of the target cell after determining that at least one of the N parameters is less than or equal to a corresponding threshold and determining that each terminal device in connected mode in the target cell is in a discontinuous reception (DRX) sleep period or that no terminal in connected mode exists in the target cell, where the first OFDM symbol carries a cell specific reference signal CRS corresponding to a first port and/or a second port.