Data retransmission method and related apparatus

When receiving a first data frame sent by a transmitting apparatus, a receiving apparatus may return error indication information including an identifier of at least one erroneous codeword group to the transmitting apparatus if it is found that an error occurs in an initial codeword of the first data frame. The transmitting apparatus may obtain the erroneous codeword group and encode the erroneous codeword group, and retransmit a part of a sub check codeword obtained through encoding to the receiving apparatus. The receiving apparatus may obtain a third check matrix based on a first check matrix, a second check matrix, and a location of the at least one erroneous codeword group in the initial codeword, and re-decode the retransmitted partial sub check codeword and content of the first data frame together based on the third check matrix, so as to obtain a correct initial codeword.