A transmission rate adjustment method and a network device, the method including obtaining, by a network device, a target data stream, where the target data stream includes a first data packet, and where the first data packet includes at least two non-idle units, and inserting or deleting a padding unit between two non-idle units of the at least two non-idle units, in response to bandwidth adjustment needing to be performed, and according to a value of the bandwidth adjustment that needs to be performed, where the padding unit provides adaption to a difference between a bandwidth of an upstream transmission channel of the network device and a bandwidth of a downstream transmission channel of the network device.