Embodiments of the present invention disclose a data frame transmission method and a related device. The method includes: first, generating a data frame, where an overhead area of the data frame includes a target bit, the target bit simultaneously indicates at least two multiframes, the multiframe includes a plurality of consecutive data frames, different multiframes include different quantities of data frames, different overhead information is inserted into the different multiframes, and the data frame is an optical transport network OTN data frame; and then sending the data frame.