Embodiments of the present invention provide a method and an apparatus for increasing and decreasing variable optical channel bandwidth. The method for increasing includes: sending a higher order optical channel data unit (HO ODU) frame to which a timeslot increase indication is added to a second NE; starting from a next HO ODU frame, mapping, by an NE, a bit stream formed by a flexible optical transport data unit (ODUflex) bit stream at a first rate and an idle data bit stream to Y timeslots of the HO ODU frame; sending an ODUflex frame to which a rate increase indication is added to the second NE; and starting from a next ODUflex frame, mapping an ODUflex bit stream at a second rate to the Y timeslots of the HO ODU frame.