This application discloses a retransmission method and an apparatus. The method includes: obtaining a first bit sequence and a number E of to-be-retransmitted bits, performing second channel encoding based on the first bit sequence to obtain a second bit sequence, and performing retransmission based on the second bit sequence. The first bit sequence is obtained by performing first channel encoding based on K information bits, a length of the first bit sequence is N, N, E, and K are all integers greater than or equal to 1, and the second bit sequence includes the E to-be-retransmitted bits. According to the method, a code length can be flexibly extended based on different numbers E of to-be-retransmitted bits.