Disclosed are a data retransmission decoding method, apparatus and system, and a communication device. The method includes: obtaining retransmitted data to be decoded, the retransmitted data to be decoded including a code block to be decoded (S102); according to stored check state information of a previously decoded code block, judging whether the code block to be decoded includes a target code block required to be decoded again (S104); and if the code block to be decoded includes the target code block required to be decoded again, merging and decoding a currently stored first code block and the target code block based on a predetermined decoding parameter (S106), wherein the first code block is a code block corresponding to the target code block.