A method and system for controlling the selection of the transmitting path for the media flow in NGN. First, the application layer signaling analysis module in the service control device analyzes the application layer signaling, and determines the required information for transmitting the service media flow, and provides it to the policy determining function entity; the policy determining function entity determines the forward path identification information for transmitting the media flow according to the required information for transmitting the media flow and the policy information stored in itself, and provides it to the flow transmitting control module; the flow transmitting control module in the network edge device performs the transmitting control for the media flow according to the forward path identification information, and guides the media flow to the corresponding forward path. This invention can realize the selection of the core network in which the NGN service user level and the session level have the fine granulation and the selection of the core network path, and enhance the QoS of the NGN and the ability of the security assurance.