At least a method and a device for transmitting data are disclosed. The method includes obtaining n FlexE signal streams, where a transmission rate of each FlexE signal stream is a first rate, distributing an ith FlexE signal stream into m signal sub-streams, where each of the m signal sub-streams carries a first identifier, which indicate that the signal sub-stream carrying the first identifier belongs to the ith FlexE signal stream, inserting a preset quantity of padding code blocks into each of the m signal sub-streams, to obtain m padded signal sub-streams, so that transmission rate of each of the m padded signal sub-streams is equal to that of a first optical module, where the rate of the first optical module is greater than the first rate/m, and less than the first rate, and sending the m padded signal sub-streams by using m first optical modules.