This application provides a data stream processing method and a network element device. The method includes: obtaining, by a first network element device, a first data stream, where the first data stream includes a first data unit and a first data padding unit; and adjusting, by the first network element device, a quantity of second data padding units in the first data stream, where a relative position of the first data unit and the first data padding unit in the first data stream is the same as a relative position of the first data unit and the first data padding unit in a second data stream, and the second data stream is an adjusted first data stream. When adjusting a rate, the first network element device does not add or delete the first data padding unit in the first data stream.