Recently, the world-wide huge energy consumption of Internet has incurred a sustained attention, and energy saving has turned into one of the hot issues in the upcoming future networks in the past few years. A network-level green energy-saving mechanism over the backbone networks is proposed in this study: for one thing, in the global view, a smallest remaining capacity first (SRCF) based green routing algorithm is used to plan the global routing paths in the networks, which makes the number of the bundled links powered minimum and thus realizes the first step of energy saving; for the other, in the local view, a green-best fit deceasing (G-BFD) algorithm is used to gather traffic loads flowing through a bundled link to the smallest set of physical links, which enables the physical links powered off as much as possible and thus implements the further energy saving. In addition to saving energy, the proposed mechanism pays attention to guaranteeing the user's requirements on quality of service (QoS), that is, the mechanism maximizes the benefits of energy saving under the premise of providing QoS guarantee. In order to evaluate the proposed mechanism in the study comprehensively, the topologies of three typical backbone networks, namely CERNET2, GéANT, and INTERNET2, are chosen. Under the different traffic status of high load, medium load, and low load, the proposed mechanism is compared with the other three energy-saving mechanisms with regard to network power consumption and network performance (as for average routing hops, the number of physical links powered off, routing success rate, and running time) and further the differences among them are analyzed fully. The results of simulation indicate that the proposed mechanism has a remarkable energy saving effect and a satisfactory performance.