A data transmission method, applied to a terminal, and comprising: establishing (S401, S1001, S1201), by the terminal, a wireless connection to another terminal; establishing (S402, S1004, S1204), by the terminal, a wired universal serial bus USB connection to the other terminal; displaying, by the terminal, a first interface, wherein the first interface comprises at least one piece of candidate data; selecting to-be-transmitted data from the at least one piece of candidate data in response to a first input of a user on the first interface; sending, in response to a second input of the user on the first interface, by the terminal, the to-be-transmitted data to the other terminal comprising sending a first data of the to-be-transmitted data to the other terminal through the wireless connection and a second data of the to-be-transmitted data to the other terminal through the wired USB connection simultaneously; and characterized by after the establishing, by the terminal, of the wired USB connection to the other terminal, supplying, by the terminal, power to the other terminal through the wired USB connection; and after the supplying, by the terminal, of the power to the other terminal through the wired USB connection, obtaining a remaining battery level of the terminal and a remaining battery level of the other terminal using the established wireless connection or the established wired USB connection; switching a host-slave relationship of the wired USB connection based on the obtained remaining battery level of the terminal and the obtained remaining battery level of the other terminal without changing the data transmission direction between the terminal and the other terminal such that interruption of the sending of the to-be-transmitted data is avoided. establishing (S401, S1001, S1201), by the terminal, a wireless connection to another terminal; establishing (S402, S1004, S1204), by the terminal, a wired universal serial bus USB connection to the other terminal; displaying, by the terminal, a first interface, wherein the first interface comprises at least one piece of candidate data; selecting to-be-transmitted data from the at least one piece of candidate data in response to a first input of a user on the first interface; sending, in response to a second input of the user on the first interface, by the terminal, the to-be-transmitted data to the other terminal comprising sending a first data of the to-be-transmitted data to the other terminal through the wireless connection and a second data of the to-be-transmitted data to the other terminal through the wired USB connection simultaneously; and characterized by after the establishing, by the terminal, of the wired USB connection to the other terminal, supplying, by the terminal, power to the other terminal through the wired USB connection; and after the supplying, by the terminal, of the power to the other terminal through the wired USB connection, obtaining a remaining battery level of the terminal and a remaining battery level of the other terminal using the established wireless connection or the established wired USB connection; switching a host-slave relationship of the wired USB connection based on the obtained remaining battery level of the terminal and the obtained remaining battery level of the other terminal without changing the data transmission direction between the terminal and the other terminal such that interruption of the sending of the to-be-transmitted data is avoided.