This application provides a polar coding method, a polar decoding method, and an apparatus. A transmit end obtains K to-be-coded bits and an index set including K polar channels, where a value set of K1 indexes in the set of the K indexes or a value set of K2 indexes in the set of the K indexes is determined based on a value set of K2 of the K to-be-coded bits, and the value set of the K1 indexes and the value set of the K2 indexes are complementary sets of each other; and performs polar coding on K1 to-be-coded bits. In comparison with a conventional polar coding method and a conventional polar decoding method, the polar coding method and the polar decoding method provided in this application can achieve an effect of reducing a bit rate. A simulation result indicates that the method has better performance.