Embodiments of the present invention relate to the field of communications, and provide a network coding method, a relay apparatus and a selection apparatus, which can avoid a case that a network coding system matrix is not full rank, and improve correctness of decoding. The network coding method includes: obtaining network coding information, where the network coding information includes information of a candidate network coding vector set and a candidate transmission rate set, and transmission rates in the candidate transmission rate set are in one-to-one correspondence with network coding vectors in the candidate network coding vector set; selecting a full rank network matrix according to the network coding information; and coding received source node information according to the full rank network matrix. The network coding method, relay apparatus and selection apparatus provided in the embodiments of the present invention are used for network coding.