A method and an apparatus for transmitting a timing difference. The method includes obtaining, by a master node, a measurement value of a timing difference between a first cell and a second cell, and sending, by the master node, the measurement value of the timing difference and identification information of the second cell to a secondary node, where the first cell is a primary cell corresponding to the master node, the second cell includes a primary secondary cell corresponding to the secondary node or another cell different from the primary secondary cell, and the identification information of the second cell includes a physical cell identifier (PCI) and frequency information of the second cell.