Provided are a link capacity adjustment method and device. The method includes: a node device obtains a latency of a Physical Layer (PHY) for link capacity adjustment of a Flex Ethernet (FlexE) group; and clock offsets of all the PHYs in the FlexE group are aligned according to the obtained latency. According to embodiments of the present disclosure, the clock offsets of all the PHYs in the FlexE group are aligned, thereby preventing data loss caused by the clock offsets of the PHYs in the FlexE group during link capacity adjustment.