Embodiments of the present invention provide a method, an apparatus, and a system for transmitting data in the Ethernet, and relate to the field of Ethernet communications, so as to reduce the complexity of data processing while achieving transmission of high-rate data. The method includes: receiving to-be-transmitted data; determining a first integral number according to a data amount of the received to-be-transmitted data and a transmission bandwidth of an electrophysical sub-channel; distributing the to-be-transmitted data to a first integral number of electrophysical sub-channels; performing, by the first integral number of electrophysical sub-channels, coding and scrambling processing on the to-be-transmitted data; and sending after processing, by a second integral number of photophysical sub-channels, data from the first integral number of electrophysical sub-channels.