Methods and apparatuses are provided for constructing a punctured polar code in the encoding and decoding field to improve decoding performance of a punctured polar code and reduce a frame error rate of the punctured polar code. The method is as follows: comparing a phase sequence number of a current bit channel with a period index of a puncturing pattern to obtain a comparison result; obtaining a transition probability of the bit channel according to the comparison result and bit parity conditions of a sequence number of the bit channel in each phase; obtaining a reliability value of each bit channel according to the transition probability; and determining an information bit index set according to the reliability values.