A data sending method, comprising: sending a 1 st polar-coded code word, wherein the 1 st code word comprises n 1 st information bits carrying user data, and the 1 st information bits comprise first n bits in bits of the 1 st code word that are sorted by channel capacity in descending order; and sending a 2 nd polar-coded code word after the 1 st code word is sent, wherein the 2 nd code word comprises p 2 nd information bits carrying user data, each 2 nd information bit carries same user data as one uniquely corresponding 1 st retransmission bit, the 2 nd information bits comprise first p bits in bits of the 2 nd code word that are sorted by channel capacity in descending order, the 1 st retransmission bits comprise first p bits in the 1 st information bits sorted by channel capacity in ascending order, n is a positive integer, and p is a positive integer not greater than n, wherein the method further comprises: sending an (i+1) th code word after an i th code word is sent, wherein the (i+1) th code word comprises q (i+1) th information bits carrying user data, and each (i+1) th information bit carries same user data as one uniquely corresponding i th retransmission bit; and the (i+1) th information bits comprise first q bits in bits of the (i+1) th code word that are sorted by channel capacity in descending order, the i th retransmission bits comprise first q bits in bits that carry user data in an i th combined code word and that are sorted by channel capacity in ascending order, the i th combined code word is generated by combining the i th code word and an (i-1) th combined code word, i=2, 3,..., k, a 1 st combined code word is the 1 st code word, k is a maximum quantity of retransmissions, q is a positive integer not greater than n, and both the i th code word and the (i+1) th code word are polar-coded code words. sending a 1 st polar-coded code word, wherein the 1 st code word comprises n 1 st information bits carrying user data, and the 1 st information bits comprise first n bits in bits of the 1 st code word that are sorted by channel capacity in descending order; and sending a 2 nd polar-coded code word after the 1 st code word is sent, wherein the 2 nd code word comprises p 2 nd information bits carrying user data, each 2 nd information bit carries same user data as one uniquely corresponding 1 st retransmission bit, the 2 nd information bits comprise first p bits in bits of the 2 nd code word that are sorted by channel capacity in descending order, the 1 st retransmission bits comprise first p bits in the 1 st information bits sorted by channel capacity in ascending order, n is a positive integer, and p is a positive integer not greater than n, wherein the method further comprises: sending an (i+1) th code word after an i th code word is sent, wherein the (i+1) th code word comprises q (i+1) th information bits carrying user data, and each (i+1) th information bit carries same user data as one uniquely corresponding i th retransmission bit; and the (i+1) th information bits comprise first q bits in bits of the (i+1) th code word that are sorted by channel capacity in descending order, the i th retransmission bits comprise first q bits in bits that carry user data in an i th combined code word and that are sorted by channel capacity in ascending order, the i th combined code word is generated by combining the i th code word and an (i-1) th combined code word, i=2, 3,..., k, a 1 st combined code word is the 1 st code word, k is a maximum quantity of retransmissions, q is a positive integer not greater than n, and both the i th code word and the (i+1) th code word are polar-coded code words. sending an (i+1) th code word after an i th code word is sent, wherein the (i+1) th code word comprises q (i+1) th information bits carrying user data, and each (i+1) th information bit carries same user data as one uniquely corresponding i th retransmission bit; and the (i+1) th information bits comprise first q bits in bits of the (i+1) th code word that are sorted by channel capacity in descending order, the i th retransmission bits comprise first q bits in bits that carry user data in an i th combined code word and that are sorted by channel capacity in ascending order, the i th combined code word is generated by combining the i th code word and an (i-1) th combined code word, i=2, 3,..., k, a 1 st combined code word is the 1 st code word, k is a maximum quantity of retransmissions, q is a positive integer not greater than n, and both the i th code word and the (i+1) th code word are polar-coded code words.