A method for a node device to enter or exit a power-saving mode and a node device are disclosed. The method for a node device to enter a power-saving mode includes: the node device detecting characteristics of a reverse power supply signal provided by a customer premise equipment, and if a condition of entering a power-saving mode is satisfied, the node device entering the power-saving mode. The method for a node device to exit a power-saving mode includes: the node device in a power-saving mode exiting the power-saving mode after detecting that a customer premise equipment starts reverse power supply to the node device. The node device includes a reverse power supply unit, a power source unit, a control unit, and a transceiver unit.