An encoding method, an apparatus, a system, and a chip. In the method, a block pair is sent through one serial channel, where the block pair includes a first block and a second block, a length of the first block is the same as a length of the second block, and the first block indicates a type of the second block. The type of the second block is indicated by the first block, and the second block does not need to include content indicating the type of the second block. The second block can carry other content other than the content indicating the type of the second block and the length of the first block is the same as the length of the second block.