A method, a network device, and a system for synchronization between network devices are provided. The method includes: establishing, by a first network device, an inband synchronization channel to a second network device in a MPLS-TP network, where the inband synchronization channel is a channel on a data plane, and the first network device and the second network device are included in a same backup group; sending, a first synchronization packet to the second network device through the inband synchronization channel, where the first synchronization packet carries synchronization information of the first network device, and the synchronization information of the first network device includes configuration information or status information of the first network device. The present disclosure can implement synchronization between network devices on an MPLS-TP network that does not have a control plane.