This disclosure provides a decoding method and apparatus in the communications field. The method includes: extracting at least one piece of prior information from at least one first transport block that has been successfully decoded, and assembling the at least one piece of prior information into a prior information set, where one piece of prior information includes header information of a transmission protocol layer of one first transport block; when a to-be-decoded second transport block sent by a transmit end is received, selecting first prior information from the prior information set, where the second transport block is a transport block obtained by the transmit end by coding a third transport block; and decoding the second transport block based on the first prior information and first demodulation information of the second transport block, to obtain the third transport block.