A data transmission method and apparatus, where the method comprises checking full-bandwidth transmission paths of a bus, and When a fault occurs in the full-bandwidth transmission paths and a quantity of faulty full-bandwidth transmission paths is less than or equal to M, selecting N full-bandwidth transmission paths from full-bandwidth transmission paths that are not faulty to transmit a data unit, and when a fault occurs in the full-bandwidth transmission paths and a quantity of faulty full-bandwidth transmission paths is greater than M, reconfiguring a size of a data unit according to a quantity of full-bandwidth transmission paths that are not faulty and a target burst quantity.