A channel establishment method and device are provided. The method includes: establishing a media channel between a first node and a second node; establishing a signal channel between a third node and a fourth node after the media channel is established, the signal channel passes a frequency slot matrix of one or more intermediate nodes between the third node and the fourth node and a traffic engineering link between any two nodes; and allocating frequency spectrum to the signal channel from available frequency spectrum of the traffic engineering link, wherein the frequency spectrum allocated includes multiple split 50 GHz frequency spectrums which bear one optical channel and each of which only includes single optical carrier. The solution addresses the problem of how to effectively plan and manage frequency spectrum for an introduced flexible grid technology, improves waveband spectrum efficiency and achieves the compatibility to 50 GHz transmission technology of existing DWDM systems.