A data transmission method, characterized in that the method comprises: determining, by a transmitting device, a long training sequence set, wherein the long training sequence set comprises at least two long training sequences; determining a mapping relationship between each long training sequence in the long training sequence set and first sub-identity information in identity information of each receiving device in a communications system, wherein one piece of identity information is used to uniquely indicate one receiving device in the communications system, and the first sub-identity information is a part or all of the identity information; when data needs to be transmitted to a target receiving device, selecting a target long training sequence from the long training sequence set according to first sub-identity information of the target receiving device and the mapping relationship; performing encapsulation processing on the data according to the target long training sequence to generate a data packet, so as to carry, in a long training sequence field at a physical layer of the data packet, a long training sequence symbol used to indicate the target long training sequence; and sending the data packet to the target receiving device; wherein when the target receiving device is one receiving device in the communications system, the selecting the target long training sequence from the long training sequence set according to first sub-identity information of the target receiving device and the mapping relationship comprises: selecting, from the long training sequence set according to the first sub-identity information of the target receiving device and the mapping relationship, a long training sequence corresponding to only the first sub-identity information of the target receiving device as the target long training sequence. determining, by a transmitting device, a long training sequence set, wherein the long training sequence set comprises at least two long training sequences; determining a mapping relationship between each long training sequence in the long training sequence set and first sub-identity information in identity information of each receiving device in a communications system, wherein one piece of identity information is used to uniquely indicate one receiving device in the communications system, and the first sub-identity information is a part or all of the identity information; when data needs to be transmitted to a target receiving device, selecting a target long training sequence from the long training sequence set according to first sub-identity information of the target receiving device and the mapping relationship; performing encapsulation processing on the data according to the target long training sequence to generate a data packet, so as to carry, in a long training sequence field at a physical layer of the data packet, a long training sequence symbol used to indicate the target long training sequence; and sending the data packet to the target receiving device; wherein when the target receiving device is one receiving device in the communications system, the selecting the target long training sequence from the long training sequence set according to first sub-identity information of the target receiving device and the mapping relationship comprises: selecting, from the long training sequence set according to the first sub-identity information of the target receiving device and the mapping relationship, a long training sequence corresponding to only the first sub-identity information of the target receiving device as the target long training sequence.