A data mapping method for an Optical channel Transport Unit-k, OTUK, wherein the method comprises: generating , by an OTUk writing control module , a writing control signal for OTUk data according to a valid signal for the OTUk data and a data storage state, which is a level of storage data, of a data storage First Input First Output, FIFO, module , writing the OTUk data to the data storage FIFO module ; outputting , by an OTUk reading control module , a reading control signal for the OTUk data according to frame header information of an OTUk superframe, OTUku, provided by an OTUku frame header and multi-frame generation module and the data storage state of the data storage FIFO module , controlling the data storage FIFO module to read and send the OTUk data to an OTUku overhead and data insertion module , generating a mapping adjustment overhead from an OTUk to an OTUku, and sending the overhead to the OTUku overhead and data insertion module ; wherein the generating the mapping adjustment overhead from the OTUk to the OTUku, comprises: executing negative justification when FIFO storage data is greater than or equal to 2/3 of an FIFO depth; or executing positive justification when the FIFO storage data is less than 1/3 of the FIFO depth; and inserting , by the OTUku overhead and data insertion module , the OTUk data output by the data storage FIFO module , the mapping adjustment overhead output by the OTUk reading control module and OTUku frame header and multi-frame information generated by the OTUku frame header and multi-frame generation module to a corresponding location of the OTUku frame, and generating an OTUku data frame. generating , by an OTUk writing control module , a writing control signal for OTUk data according to a valid signal for the OTUk data and a data storage state, which is a level of storage data, of a data storage First Input First Output, FIFO, module , writing the OTUk data to the data storage FIFO module ; outputting , by an OTUk reading control module , a reading control signal for the OTUk data according to frame header information of an OTUk superframe, OTUku, provided by an OTUku frame header and multi-frame generation module and the data storage state of the data storage FIFO module , controlling the data storage FIFO module to read and send the OTUk data to an OTUku overhead and data insertion module , generating a mapping adjustment overhead from an OTUk to an OTUku, and sending the overhead to the OTUku overhead and data insertion module ; wherein the generating the mapping adjustment overhead from the OTUk to the OTUku, comprises: executing negative justification when FIFO storage data is greater than or equal to 2/3 of an FIFO depth; or executing positive justification when the FIFO storage data is less than 1/3 of the FIFO depth; and inserting , by the OTUku overhead and data insertion module , the OTUk data output by the data storage FIFO module , the mapping adjustment overhead output by the OTUk reading control module and OTUku frame header and multi-frame information generated by the OTUku frame header and multi-frame generation module to a corresponding location of the OTUku frame, and generating an OTUku data frame. <EOS>