1. A method for selecting a real-time service data transmission path based on label switching, applied to an independent bearer control layer comprising more than one bearer network resource manager which is established between a service control layer and a bearer network, each of the more than one bearer network resource manager corresponding to one domain, and when a source bearer network resource manager receives a connection resource request for a real-time service from the service control layer, the method comprising: from the source bearer network resource manager to a destination bearer network resource manager hop by hop, determining, by each source bearer network resource manager except the destination bearer network resource manager, an inter-domain label switching path (LSP) between a local domain and a next-hop domain, and sending a connection resource request to a next hop bearer network resource manager; and, from the destination bearer network resource manager to the source bearer network resource manager hop by hop, sending, by each bearer network resource manager except the source bearer network resource manager, the determined inter-domain LSP and an intra-domain LSP of the local domain in a connection resource response to a previous hop bearer network resource manager; receiving, by the source bearer network resource manager, the connection resource response, obtaining a whole LSP aggregate for the connection resource request, which is from the source bearer network resource manager to the destination bearer network resource manager.