Embodiments of this application provide a polar code retransmission method and apparatus, to reduce retransmission complexity and improve transmission performance. The method includes: determining a first polar channel sequence including N polar channels and reliability of each of the N polar channels; determining, based on a coding parameter for an mth data transmission, a quantity Km of information bits that need to be transmitted during the mth data transmission, where the coding parameter includes at least one of the quantity of information bits and a code rate; determining Km polar channels with highest reliability in the first polar channel sequence; determining Km information bits based on locations, of information bits that need to be transmitted during first m−1 data transmissions, in the first polar channel sequence; and mapping the Km information bits to the Km polar channels for transmission.