A bandwidth adjusting method, comprising: sending, by an upstream ingress unit of a local node, a group of multi-channel parallel basic switch cells to all downstream branch egress units of the local node, wherein a first adjustment signaling is carried in the group of multi-channel parallel basic switch cells and is used for indicating unidirectional addition or removal of a basic switch cell; returning, by downstream branch egress units that receive the group of multi-channel parallel basic switch cells carrying the first adjustment signaling, unidirectional adjustment response statuses that carry respective downstream branch egress unit identifiers and are used for indicating the reception of the first adjustment signaling; sending, by the upstream ingress unit, a first normal signaling to all the downstream branch egress units when determining that the first adjustment response statuses returned by all the downstream branch egress units are reception acknowledgement by performing a polling detection on the unidirectional adjustment response statuses returned by the downstream branch egress units according to a downstream branch egress unit list of the local node, wherein the downstream branch egress unit list stores a corresponding relation between an upstream ingress unit identifier and all downstream branch egress unit identifiers; and after receiving the first normal signaling, adding or removing, by each downstream branch egress unit, the basic switch cell into or from a next group of multi-channel parallel basic switch cells according to the first adjustment signaling, adjusting a time slot of a high order optical channel data unit sent by the downstream branch egress unit to a downstream node, and instructing the downstream node to adjust the time slot of the received high order optical channel data unit. sending, by an upstream ingress unit of a local node, a group of multi-channel parallel basic switch cells to all downstream branch egress units of the local node, wherein a first adjustment signaling is carried in the group of multi-channel parallel basic switch cells and is used for indicating unidirectional addition or removal of a basic switch cell; returning, by downstream branch egress units that receive the group of multi-channel parallel basic switch cells carrying the first adjustment signaling, unidirectional adjustment response statuses that carry respective downstream branch egress unit identifiers and are used for indicating the reception of the first adjustment signaling; sending, by the upstream ingress unit, a first normal signaling to all the downstream branch egress units when determining that the first adjustment response statuses returned by all the downstream branch egress units are reception acknowledgement by performing a polling detection on the unidirectional adjustment response statuses returned by the downstream branch egress units according to a downstream branch egress unit list of the local node, wherein the downstream branch egress unit list stores a corresponding relation between an upstream ingress unit identifier and all downstream branch egress unit identifiers; and after receiving the first normal signaling, adding or removing, by each downstream branch egress unit, the basic switch cell into or from a next group of multi-channel parallel basic switch cells according to the first adjustment signaling, adjusting a time slot of a high order optical channel data unit sent by the downstream branch egress unit to a downstream node, and instructing the downstream node to adjust the time slot of the received high order optical channel data unit.