This application provides a polar encoding method and apparatus. The method can include obtaining a basic sequence, where the basic sequence includes N0 subchannel numbers. The method can also include sequentially reading first subchannel numbers from the basic sequence, and sequentially reading 2m second subchannel numbers from the basic sequence starting from an Mth subchannel number based on the first subchannel number read each time; and adding q*N0 to each of the 2m second subchannel numbers to obtain 2m third subchannel numbers. Furthermore, the method can include constructing a polar code by using subchannels corresponding to the 2m third subchannel numbers as information bits. A polar code with another code length is constructed based on a sequence with a length of N0. A length of a polar code that needs to be stored is therefore reduced, which reduces complexity and is also easy to implement.