A data transmission method comprising: when no data is to be transmitted or received, receiving, by the terminal, first indication information in a first cell using a first frequency band, the first indication information being configured to instruct the terminal receiving the first indication information to perform data transmission using a second frequency band when there is data to be transmitted or received; determining, by the terminal, one or more second cells using the second frequency band to be a target cell according to the first indication information; performing, by the terminal, synchronization with the target cell; and when there is data to be transmitted or received, performing, by the terminal, data transmission with the target cell using the second frequency band; wherein performing, by the terminal, synchronization with the target cell comprises: receiving, by the terminal, downlink synchronization information of the first cell in the first cell; receiving, by the terminal, at least one downlink synchronization offset information transmitted by a first base station through the first cell and corresponding to the at least one second cell, each downlink synchronization offset information comprising a time offset between timing of the corresponding second cell and timing of the first cell, and the first base station being a base station containing the first cell; determining, by the terminal, the downlink synchronization information of the target cell according to the downlink synchronization offset information of the at least one second cell; and performing, the terminal, downlink synchronization with the target cell according to the downlink synchronization information of the target cell. when no data is to be transmitted or received, receiving, by the terminal, first indication information in a first cell using a first frequency band, the first indication information being configured to instruct the terminal receiving the first indication information to perform data transmission using a second frequency band when there is data to be transmitted or received; determining, by the terminal, one or more second cells using the second frequency band to be a target cell according to the first indication information; performing, by the terminal, synchronization with the target cell; and when there is data to be transmitted or received, performing, by the terminal, data transmission with the target cell using the second frequency band; wherein performing, by the terminal, synchronization with the target cell comprises: receiving, by the terminal, downlink synchronization information of the first cell in the first cell; receiving, by the terminal, at least one downlink synchronization offset information transmitted by a first base station through the first cell and corresponding to the at least one second cell, each downlink synchronization offset information comprising a time offset between timing of the corresponding second cell and timing of the first cell, and the first base station being a base station containing the first cell; determining, by the terminal, the downlink synchronization information of the target cell according to the downlink synchronization offset information of the at least one second cell; and performing, the terminal, downlink synchronization with the target cell according to the downlink synchronization information of the target cell. receiving, by the terminal, downlink synchronization information of the first cell in the first cell; receiving, by the terminal, at least one downlink synchronization offset information transmitted by a first base station through the first cell and corresponding to the at least one second cell, each downlink synchronization offset information comprising a time offset between timing of the corresponding second cell and timing of the first cell, and the first base station being a base station containing the first cell; determining, by the terminal, the downlink synchronization information of the target cell according to the downlink synchronization offset information of the at least one second cell; and performing, the terminal, downlink synchronization with the target cell according to the downlink synchronization information of the target cell.