This application provides a coding and decoding method and apparatus. The method includes: performing polarization coding on first to-be-coded information, to obtain first coded information with a bit sequence length of M, where M is a positive integer; sending the first coded information on a first channel corresponding to the first to-be-coded information; performing polarization coding on second to-be-coded information, to obtain second coded information with a bit sequence length of 2M, where the second to-be-coded information includes the first to-be-coded information, and differences between sequence numbers of information bits corresponding to the first to-be-coded information and sequence numbers of information bits at (M+1)th to 2Mth bit positions in information bits corresponding to the second to-be-coded information are sequentially M in ascending order of sequence numbers.