A data transmission method, comprising: modulating (S201, S501, S1001, S1401) to-be-sent information bits according to a lower order constellation diagram, and generating 4m lower order modulation symbols, wherein m is an integer greater than or equal to 1; separately multiplying (S202, S502, S1002, S1402) a precoding matrix Q by a column vector comprising every four lower order modulation symbols in the 4m lower order modulation symbols, to obtain 4m to-be-sent higher order modulation symbols corresponding to a higher order constellation diagram; characterized in that the method further comprises: respectively and correspondingly sending (S203, S503, S1003, S1403) the 4m to-be-sent higher order modulation symbols on different carriers of two antennas, wherein the 4m to-be-sent higher order modulation symbols are classified into four types, a 4( i -1)+1 th higher order modulation symbol is a first higher order modulation symbol, a 4( i -1)+2 th higher order modulation symbol is a second higher order modulation symbol, a 4( i -1)+3 th higher order modulation symbol is a third higher order modulation symbol, and a 4(i-1)+4) th higher order modulation symbol is a fourth higher order modulation symbol, wherein 1≤ i ≤ l, and i is an integer, l is an integer greater than or equal to 1; and the respectively and correspondingly sending (S203, S503, S1003, S1403) the 4m to-be-sent higher order modulation symbols on different carriers of two antennas comprises: sending the first higher order modulation symbol on a first subcarrier of a first transmit antenna; sending the second higher order modulation symbol on a first subcarrier of a second transmit antenna; sending the third higher order modulation symbol on a second subcarrier of the first transmit antenna; and sending the fourth higher order modulation symbol on a second subcarrier of the second transmit antenna. modulating (S201, S501, S1001, S1401) to-be-sent information bits according to a lower order constellation diagram, and generating 4m lower order modulation symbols, wherein m is an integer greater than or equal to 1; separately multiplying (S202, S502, S1002, S1402) a precoding matrix Q by a column vector comprising every four lower order modulation symbols in the 4m lower order modulation symbols, to obtain 4m to-be-sent higher order modulation symbols corresponding to a higher order constellation diagram; characterized in that the method further comprises: respectively and correspondingly sending (S203, S503, S1003, S1403) the 4m to-be-sent higher order modulation symbols on different carriers of two antennas, wherein the 4m to-be-sent higher order modulation symbols are classified into four types, a 4( i -1)+1 th higher order modulation symbol is a first higher order modulation symbol, a 4( i -1)+2 th higher order modulation symbol is a second higher order modulation symbol, a 4( i -1)+3 th higher order modulation symbol is a third higher order modulation symbol, and a 4(i-1)+4) th higher order modulation symbol is a fourth higher order modulation symbol, wherein 1≤ i ≤ l, and i is an integer, l is an integer greater than or equal to 1; and the respectively and correspondingly sending (S203, S503, S1003, S1403) the 4m to-be-sent higher order modulation symbols on different carriers of two antennas comprises: sending the first higher order modulation symbol on a first subcarrier of a first transmit antenna; sending the second higher order modulation symbol on a first subcarrier of a second transmit antenna; sending the third higher order modulation symbol on a second subcarrier of the first transmit antenna; and sending the fourth higher order modulation symbol on a second subcarrier of the second transmit antenna. respectively and correspondingly sending (S203, S503, S1003, S1403) the 4m to-be-sent higher order modulation symbols on different carriers of two antennas, wherein the 4m to-be-sent higher order modulation symbols are classified into four types, a 4( i -1)+1 th higher order modulation symbol is a first higher order modulation symbol, a 4( i -1)+2 th higher order modulation symbol is a second higher order modulation symbol, a 4( i -1)+3 th higher order modulation symbol is a third higher order modulation symbol, and a 4(i-1)+4) th higher order modulation symbol is a fourth higher order modulation symbol, wherein 1≤ i ≤ l, and i is an integer, l is an integer greater than or equal to 1; and the respectively and correspondingly sending (S203, S503, S1003, S1403) the 4m to-be-sent higher order modulation symbols on different carriers of two antennas comprises: sending the first higher order modulation symbol on a first subcarrier of a first transmit antenna; sending the second higher order modulation symbol on a first subcarrier of a second transmit antenna; sending the third higher order modulation symbol on a second subcarrier of the first transmit antenna; and sending the fourth higher order modulation symbol on a second subcarrier of the second transmit antenna.