A data transmission method, for applying to a base station, comprising acquiring target information for indicating transmission direction from pre-configured indication unit allocation information, the target information for indicating transmission direction being configured for a terminal to determine transmission directions of uplink data transmission on an indication unit of uplink carrier and downlink data transmission on an indication unit of downlink carrier in a frequency division duplexing, FDD, mode, and sending the target information for indicating transmission direction to the terminal, to cause the terminal to determine respective transmission directions of the indication unit of uplink carrier and the indication unit of downlink carrier in the FDD mode according to the target information for indicating transmission direction, wherein the pre-configured indication unit allocation information comprises multiple pieces of information for indicating transmission direction, the target information for indicating transmission direction is one of the multiple pieces of information for indicating transmission direction, and each of the multiple pieces of information for indicating transmission direction comprises indication unit allocation information of downlink carrier and indication unit allocation information of uplink carrier; and the indication unit allocation information of downlink carrier is configured to reserve a part of resources for a downlink carrier such that a state of a time slot of the downlink carrier comprises an unknown state, and the indication unit allocation information of uplink carrier is configured to reserve a part of resources for a uplink carrier such that a state of a time slot of the uplink carrier comprises the unknown state, wherein the unknown state indicates that the time slot of the uplink or downlink carrier has not been configured for uplink transmission or downlink transmission. acquiring target information for indicating transmission direction from pre-configured indication unit allocation information, the target information for indicating transmission direction being configured for a terminal to determine transmission directions of uplink data transmission on an indication unit of uplink carrier and downlink data transmission on an indication unit of downlink carrier in a frequency division duplexing, FDD, mode, and sending the target information for indicating transmission direction to the terminal, to cause the terminal to determine respective transmission directions of the indication unit of uplink carrier and the indication unit of downlink carrier in the FDD mode according to the target information for indicating transmission direction, wherein the pre-configured indication unit allocation information comprises multiple pieces of information for indicating transmission direction, the target information for indicating transmission direction is one of the multiple pieces of information for indicating transmission direction, and each of the multiple pieces of information for indicating transmission direction comprises indication unit allocation information of downlink carrier and indication unit allocation information of uplink carrier; and the indication unit allocation information of downlink carrier is configured to reserve a part of resources for a downlink carrier such that a state of a time slot of the downlink carrier comprises an unknown state, and the indication unit allocation information of uplink carrier is configured to reserve a part of resources for a uplink carrier such that a state of a time slot of the uplink carrier comprises the unknown state, wherein the unknown state indicates that the time slot of the uplink or downlink carrier has not been configured for uplink transmission or downlink transmission.