A polar coding method performed by a communications device, the method comprising: obtaining a set of information bits; determining, based on a code length N of a polar code, that there are a total of N subchannels, corresponding to N rows of a coding matrix of the polar code respectively; calculating reliability of the subchannels, using indexes of first K subchannels of higher reliability as elements of a set of indexes of the information bits of the set of information bits, and using indexes corresponding to remaining (N - K) polarized channels as elements of a set of indexes of fixed bits; constructing at least one check equation based on a correspondence between a first subchannel of the N subchannels and at least one second subchannel that is in a second subchannel group of the N subchannels, wherein a check bit of the check equation corresponds to the first subchannel, at least one information bit of the check equation corresponds to the at least one second subchannel, a sequence number of the first subchannel is divided by a first preset value and a remainder is a second preset value, a sequence number of the at least one second subchannel is divided by a third preset value and a remainder is a fourth preset value, the sequence number of the first subchannel is greater than the sequence number of the at least one second subchannel, and the correspondence indicates that the addition of the bits of the at least one second subchannel corresponding to the at least one information bit is equal to the bit of the first subchannel corresponding to the check bit; performing parity-check encoding of the bits of the N subchannels by using the at least one check equation; and performing polar encoding on the parity-check encoded bits of the N subchannels. obtaining a set of information bits; determining, based on a code length N of a polar code, that there are a total of N subchannels, corresponding to N rows of a coding matrix of the polar code respectively; calculating reliability of the subchannels, using indexes of first K subchannels of higher reliability as elements of a set of indexes of the information bits of the set of information bits, and using indexes corresponding to remaining (N - K) polarized channels as elements of a set of indexes of fixed bits; constructing at least one check equation based on a correspondence between a first subchannel of the N subchannels and at least one second subchannel that is in a second subchannel group of the N subchannels, wherein a check bit of the check equation corresponds to the first subchannel, at least one information bit of the check equation corresponds to the at least one second subchannel, a sequence number of the first subchannel is divided by a first preset value and a remainder is a second preset value, a sequence number of the at least one second subchannel is divided by a third preset value and a remainder is a fourth preset value, the sequence number of the first subchannel is greater than the sequence number of the at least one second subchannel, and the correspondence indicates that the addition of the bits of the at least one second subchannel corresponding to the at least one information bit is equal to the bit of the first subchannel corresponding to the check bit; performing parity-check encoding of the bits of the N subchannels by using the at least one check equation; and performing polar encoding on the parity-check encoded bits of the N subchannels.