A data mapping method and a data mapping device for an optical transport network are provided. The method includes: mapping packet service data or constant bit rate data to a Super Optical Channel Data Unit (ODUS) and mapping the ODUS to a Super Optical Channel Transport Unit (OTUS); distributing the OTUS to a plurality of electrical lane signals, dividing the plurality of electrical lane signals into one or more groups and mapping the one or more groups of electrical lane signals to corresponding Super Optical Channels (OChSi), wherein rates of the ODUS and the OTUS are both N times of 100Gb/s, a rate of the OChSi is M times of 100Gb/s, tributary slot sizes of the ODUS and the OTUS are both 100Gb/s, where N is a positive integer equal to or greater than 2, i is a positive integer, and M is a positive integer equal to or greater than 1 but less than N. The present invention enables an operator to deploy a beyond-100G optical transmission system more flexibly, without being limited to select a fixed rate, and improves the spectrum utilization rate of fiber as well as the flexibility and the compatibility of a system.