A data transmission method, which can improve an error correction capability during decoding, includes: determining, by a transmit end, a target code length L and an original code length K; generating an initial code block according to the original code length K, where the initial code block includes 2K initial code words; generating a superposition code block according to the target code length and an arrangement order of the 2K initial code words in the initial code block, and superposing the initial code words and the corresponding superposition code words to generate the block code words in the block code set, so that a difference between feature code distances in the block code set is ±1 or 0, where the feature code distance is a code distance between the block code words.