A method includes: obtaining a first sequence corresponding to a basic code length N0; determining N to-be-encoded bits, where the N to-be-encoded bits include N2 fixed bits, and N is greater than the basic code length N0; extending the first sequence to obtain a second sequence; determining locations of the N2 fixed bits in the N to-be-encoded bits based on polar channel serial numbers indicated by first N2 elements in the second sequence; and performing polar encoding on the N to-be-encoded bits to obtain encoded bits. The locations of the fixed bits in the N to-be-encoded bits are determined based on the second sequence, and the second sequence is obtained by extending the first sequence corresponding to the basic code length N0.