A method and an apparatus for transmission using an interface, and a device. The method includes: obtaining a byte block stream, where byte blocks in the byte block stream are of a predetermined byte length; mapping the byte block stream to corresponding timeslots, where each timeslot corresponds to one byte block; distributing the byte block stream mapped to the timeslots; processing the distributed byte block stream based on an interface type configured for a physical interface; and sending the processed byte block stream. In the embodiments, data is transmitted based on a byte block distribution mechanism, to support different interface types, and a coupling relationship between service adaptation and a physical layer is decoupled, so that evolution and extension of transmission interface types do not affect a service adaptation procedure, thereby simplifying a transmission system.