A bandwidth adjusting method and a communication node are provided. The adjusting method includes: sending, by an upstream ingress unit, a group of multi-channel parallel basic switch cells in which adjustment signaling is carried to all downstream branch egress units; sending normal signaling when determining that adjustment response statuses returned by all the downstream branch egress units are reception acknowledgment; after receiving the normal signaling by the downstream branch egress unit, adding or removing the basic switch cell into or from a next group of multi-channel parallel basic switch cells according to the adjustment signaling; and adjusting a time slot of an HO ODU sent by the downstream branch egress unit to a downstream node, and instructing the downstream node to adjust the time slot of the HO ODU. Through the method and the communication node, lossless bandwidth adjustment in a point-to-multipoint OTN asymmetric bandwidth carrier system is implemented.