Embodiments of the present invention provide a data processing method, related device, and system for an optical transport network. The data processing method for the optical transport network includes: encapsulating service data into an optical payload unit; mapping the optical payload unit to an optical channel data unit; mapping the optical channel data unit to a payload area of an optical burst transport unit; performing electrical-optical conversion on the optical burst transport unit to form an optical burst transport unit; carrying the optical burst transport unit onto an optical timeslot of an optical burst channel; and transmitting the optical burst channel to a line. Technical solutions provided by the present invention can effectively simplify a data processing process and reduce a data processing delay.