A graceful restart (GR) method of a router, and a router and a communication network thereof are provided. The method includes the following steps. A control plane enters a GR state. Label switched path (LSP) packets sent by a neighbor router are received, and the label information of the control plane is recovered according to the LSP packets. Whether the label information is completely recovered is determined. If the label information is completely recovered, the GR state is exited, and label information of a forwarding plane is updated according to the recovered label information of the control plane. The GR method of a router, the router, and the communication network decide whether to exit the GR state by detecting whether the label information of the control plane is completely recovered. This can precisely control the time of exiting the GR state is controlled and improve the reliability of the router.