Provided are a method and a device for implementing timeslot synchronization. The method includes: a master node performing timeslot synchronization training of an OBTN according to a timeslot length of the OBTN. By adopting the solution provided by the embodiments of the present disclosure, an FDL does not need to be considered in node design, the node design is simplified, the time precision of synchronization is improved and no loss is caused to optical efficiency.