The invention discloses a data transmission method and apparatus. The method comprises the following steps: mapping data to an ODUS, and mapping the ODUS to an OTUS, wherein the rate of the ODUS and the OTUS is M 100G gigabit per second, M is a positive integer greater than or equal to 2, and the size of the branch sequence of the ODUS and the OTUS is 100 gigabit per second; distributing the OTUS on M groups of electric channel signals, wherein each group of electric channel signals are corresponding to N electric layer channels, and N is a positive integer; and mapping all the data distributed by the OTUS on the electric channel signals to the same OChS for transmission, wherein the rate of the OChS is M 100G gigabit per second. The M groups of electric channel signals are borne through a single frequency sequence or multiple non-continuous frequency sequences, each frequency sequence bears m groups of the electric channel signals, 1<=m<=M, and M is an integer. Through the method and apparatus provided by the invention, the fiber frequency spectrum utilization efficiency is improved, and the system flexibility and compatibility are enhanced.