This application provides encoding and decoding methods to reduce retransmission in satellite communication. A sending apparatus obtains an information transport block, where the information transport block includes a plurality of code blocks; and generates a redundant code block based on at least two of the plurality of code blocks. The at least two code blocks and the redundant code block are sent over a satellite channel after channel coding. A receiving apparatus receives the to-be-decoded information over the satellite channel, calculates, based on the to-be-decoded information of the at least two code blocks and the redundant code block, an a priori log-likelihood ratio of a to-be-decoded bit, and combines the a priori log-likelihood ratio and a log-likelihood ratio obtained after demodulation, to obtain a diversity gain. Decoding is performed based on the combined log-likelihood ratio. This method improves decoding accuracy and reduces the need for retransmission.