A data stream multiplexing method, comprising: determining, by a terminal, a third frequency-domain data stream, wherein the third frequency-domain data stream comprises a first frequency-domain data stream and a second frequency-domain data stream, a length of the third frequency-domain data stream is 2N, lengths of both the first frequency-domain data stream and the second frequency-domain data stream are N, the first frequency-domain data stream is obtained by performing first processing on a first source data stream having a length of N ( K - 1)/ K, the first processing comprises zero adding processing and Fourier transform processing, wherein the zero adding comprises: adding zeros based on an interval K, wherein K is an interval between two adjacent zeros in a first zero-added data stream, and the second frequency-domain data stream is obtained by performing second processing on a second source data stream having a length of N / K, and the second processing comprises cyclic extension processing, wherein the cyclic extension processing comprises repeating the second source data stream for K times, wherein N is a positive integer and K is a positive integer greater than 1, wherein data in the first frequency-domain data stream is mapped to an odd-number location in the third frequency-domain data stream, and data in the second frequency-domain data stream is mapped to an even-number location in the third frequency-domain data stream; or data in the first frequency-domain data stream is mapped to an even-number location in the third frequency-domain data stream, and data in the second frequency-domain data stream is mapped to an odd-number location in the third frequency-domain data stream; converting, by the terminal, the third frequency-domain data stream into time-domain data; and sending, by the terminal, the time-domain data to a base station. determining, by a terminal, a third frequency-domain data stream, wherein the third frequency-domain data stream comprises a first frequency-domain data stream and a second frequency-domain data stream, a length of the third frequency-domain data stream is 2N, lengths of both the first frequency-domain data stream and the second frequency-domain data stream are N, the first frequency-domain data stream is obtained by performing first processing on a first source data stream having a length of N ( K - 1)/ K, the first processing comprises zero adding processing and Fourier transform processing, wherein the zero adding comprises: adding zeros based on an interval K, wherein K is an interval between two adjacent zeros in a first zero-added data stream, and the second frequency-domain data stream is obtained by performing second processing on a second source data stream having a length of N / K, and the second processing comprises cyclic extension processing, wherein the cyclic extension processing comprises repeating the second source data stream for K times, wherein N is a positive integer and K is a positive integer greater than 1, wherein data in the first frequency-domain data stream is mapped to an odd-number location in the third frequency-domain data stream, and data in the second frequency-domain data stream is mapped to an even-number location in the third frequency-domain data stream; or data in the first frequency-domain data stream is mapped to an even-number location in the third frequency-domain data stream, and data in the second frequency-domain data stream is mapped to an odd-number location in the third frequency-domain data stream; converting, by the terminal, the third frequency-domain data stream into time-domain data; and sending, by the terminal, the time-domain data to a base station. adding zeros based on an interval K, wherein K is an interval between two adjacent zeros in a first zero-added data stream, and the second frequency-domain data stream is obtained by performing second processing on a second source data stream having a length of N / K, and the second processing comprises cyclic extension processing, wherein the cyclic extension processing comprises repeating the second source data stream for K times, wherein N is a positive integer and K is a positive integer greater than 1, wherein data in the first frequency-domain data stream is mapped to an odd-number location in the third frequency-domain data stream, and data in the second frequency-domain data stream is mapped to an even-number location in the third frequency-domain data stream; or data in the first frequency-domain data stream is mapped to an even-number location in the third frequency-domain data stream, and data in the second frequency-domain data stream is mapped to an odd-number location in the third frequency-domain data stream; converting, by the terminal, the third frequency-domain data stream into time-domain data; and sending, by the terminal, the time-domain data to a base station.