A method for intercommunicating between a private network user and a network with QoS guarantee, comprising: receiving, by an Application Function, AF, entity of the network with QoS guarantee, a signaling message transmitted from the private network user, the signaling message includes identity information of the private network user, and the identity information includes a private address of the private network user; transmitting, by the AF entity, a request for applying public address, to a Policy Decision Function, PDF, or a Bearer Control Function, BCF, according to the signaling message transmitted from the private network user; said request for applying a public address carries the private address of the private network user, and applying, by the PDF or the BCF, for a public address for the private network user, from an address translation gateway, and allocating, by the address translation gateway, a public address for the private network user and returns the allocated public address to the PDF or the BCF; and the PDF or the BCF returns the allocated public address to the AF entity for saving, and saves the allocated public network address on the PDF and the BCF; and establishing, by the AF entity or the address translation gateway, a correspondence between the private address of the private network user and the public address, wherein the PDF or the BCF determines the allocated public address of the private network user according to saved correspondence between private address and public address on the PDF or BCF; and upon receiving the public address, initiating, by the AF entity, a QoS resource request, to the PDF or the BCF, where a media stream address to be carried in the QoS resource request is the allocated public address; implementing, by the PDF or the BCF, end-to-end signaling interaction and corresponding resource allocation directly using the public address allocated to the private network user; returning, by the PDF or the BCF, the resource allocation result information to the AF entity. receiving, by an Application Function, AF, entity of the network with QoS guarantee, a signaling message transmitted from the private network user, the signaling message includes identity information of the private network user, and the identity information includes a private address of the private network user; transmitting, by the AF entity, a request for applying public address, to a Policy Decision Function, PDF, or a Bearer Control Function, BCF, according to the signaling message transmitted from the private network user; said request for applying a public address carries the private address of the private network user, and applying, by the PDF or the BCF, for a public address for the private network user, from an address translation gateway, and allocating, by the address translation gateway, a public address for the private network user and returns the allocated public address to the PDF or the BCF; and the PDF or the BCF returns the allocated public address to the AF entity for saving, and saves the allocated public network address on the PDF and the BCF; and establishing, by the AF entity or the address translation gateway, a correspondence between the private address of the private network user and the public address, wherein the PDF or the BCF determines the allocated public address of the private network user according to saved correspondence between private address and public address on the PDF or BCF; and upon receiving the public address, initiating, by the AF entity, a QoS resource request, to the PDF or the BCF, where a media stream address to be carried in the QoS resource request is the allocated public address; implementing, by the PDF or the BCF, end-to-end signaling interaction and corresponding resource allocation directly using the public address allocated to the private network user; returning, by the PDF or the BCF, the resource allocation result information to the AF entity.