A reference signal sequence mapping method, comprising: determining, by a sending device, a first multiplexing set based on a first modulation symbol set and a first reference signal sequence; determining, by the sending device, a second multiplexing set based on a second modulation symbol set and a second reference signal sequence, wherein both the first modulation symbol set and the second modulation symbol set comprise at least one modulation symbol, and the first reference signal sequence and the second reference signal sequence meet orthogonality or conjugate orthogonality; and obtaining, by the sending device, a first single-carrier time domain symbol, a second single-carrier time domain symbol, a third single-carrier time domain symbol, and a fourth single-carrier time domain symbol based on the first multiplexing set and the second multiplexing set, and sending the first single-carrier time domain symbol, the second single-carrier time domain symbol, the third single-carrier time domain symbol, and the fourth single-carrier time domain symbol; characterized in that a sum of a start index of the first reference signal sequence in the first multiplexing set and a start index of the second reference signal sequence in the second multiplexing set is equal to N, wherein N is a length of the first multiplexing set and a length of the second multiplexing set, and N is an integer greater than 0 and is a length of a subsequent discrete Fourier transform; and the obtaining, by the sending device, a first single-carrier time domain symbol, a second single-carrier time domain symbol, a third single-carrier time domain symbol, and a fourth single-carrier time domain symbol based on the first multiplexing set and the second multiplexing set comprises: performing, by the sending device, space-time block code, STBC, encoding on the first multiplexing set and the second multiplexing set, to obtain a first vector, a second vector, a third vector, and a fourth vector; and obtaining, by the sending device, the first single-carrier time domain symbol, the second single-carrier time domain symbol, the third single-carrier time domain symbol, and the fourth single-carrier time domain symbol based on the first vector, the second vector, the third vector, and the fourth vector. determining, by a sending device, a first multiplexing set based on a first modulation symbol set and a first reference signal sequence; determining, by the sending device, a second multiplexing set based on a second modulation symbol set and a second reference signal sequence, wherein both the first modulation symbol set and the second modulation symbol set comprise at least one modulation symbol, and the first reference signal sequence and the second reference signal sequence meet orthogonality or conjugate orthogonality; and obtaining, by the sending device, a first single-carrier time domain symbol, a second single-carrier time domain symbol, a third single-carrier time domain symbol, and a fourth single-carrier time domain symbol based on the first multiplexing set and the second multiplexing set, and sending the first single-carrier time domain symbol, the second single-carrier time domain symbol, the third single-carrier time domain symbol, and the fourth single-carrier time domain symbol; characterized in that a sum of a start index of the first reference signal sequence in the first multiplexing set and a start index of the second reference signal sequence in the second multiplexing set is equal to N, wherein N is a length of the first multiplexing set and a length of the second multiplexing set, and N is an integer greater than 0 and is a length of a subsequent discrete Fourier transform; and the obtaining, by the sending device, a first single-carrier time domain symbol, a second single-carrier time domain symbol, a third single-carrier time domain symbol, and a fourth single-carrier time domain symbol based on the first multiplexing set and the second multiplexing set comprises: performing, by the sending device, space-time block code, STBC, encoding on the first multiplexing set and the second multiplexing set, to obtain a first vector, a second vector, a third vector, and a fourth vector; and obtaining, by the sending device, the first single-carrier time domain symbol, the second single-carrier time domain symbol, the third single-carrier time domain symbol, and the fourth single-carrier time domain symbol based on the first vector, the second vector, the third vector, and the fourth vector. performing, by the sending device, space-time block code, STBC, encoding on the first multiplexing set and the second multiplexing set, to obtain a first vector, a second vector, a third vector, and a fourth vector; and obtaining, by the sending device, the first single-carrier time domain symbol, the second single-carrier time domain symbol, the third single-carrier time domain symbol, and the fourth single-carrier time domain symbol based on the first vector, the second vector, the third vector, and the fourth vector.