A method, device and system for a cell handover in a telecommunication system supporting carrier aggregation. The method may include: a Base Station (BS) determines that whether carrier components corresponding to one or more cells to be accessed are in the same frequency band, wherein the one or more cells to be accessed belong to a target BS, and are selected by a terminal which needs to perform the cell handover and is served by the BS; if yes, the BS encapsulates configuration information of all the cells in the one or more cells to be accessed in a handover command for initiating cell handover; otherwise, the BS encapsulates configuration information of one or more cells in the one or more cells to be accessed in the handover command, and sends the handover command to the target BS.