The present invention relates to the field of communications network technologies, and discloses a polar code retransmission method and apparatus, which can improve HARQ performance. In embodiments of the present invention, some information bits of a first polar code are encoded to obtain a second polar code, where the first polar code is a code word that is transmitted for the first time; modulo-2 addition is performed on the first polar code and the second polar code to obtain a third polar code; and the third polar code is sent as a to-be-retransmitted code word. The solutions provided in the embodiments of the present invention are applicable when a polar code is retransmitted.