Provided are a method and device for mapping, multiplexing, demapping and demultiplexing data are provided. The method includes: mapping an Ethernet service data stream the rate of which is m*100 Gb/s sequentially into m Optical Payload Unit Sub-frames (OPUC) and multiplexing the m OPUC into an Optical Payload Unit Frame (OPUCm) the rate of which is m*100 Gb/s according to the way of byte interleave; and adding an Optical Channel Data Unit (ODU) overhead to the head of the OPUCm to obtain an Optical Channel Data Unit Frame (ODUCm) the rate of which is m*100 Gb/s, wherein the frame structure of the OPUC consists of 4 rows and 3810 columns; the frame structure of the OPUCm consists of 4 rows and 3810*m columns; and the frame structure of the ODUCm consists of 4 rows and 3824*m columns, wherein m is a positive integer. The present disclosure improves the spectrum efficiency of optical fibers and the systematic flexibility and the compatibility.