A signalling exchange method for guaranteeing Internet Protocol (IP) Quality of Service (QoS), including: after a Call Agent (CA) receives a request from a source User Agent (UA) for transferring a user service stream, sending a QoS resource request from the CA to the bearer control layer; allocating resources for the user service stream on the bearer control layer, and carrying out flow mapping for an Edge Router (ER) according to the resource allocation result; after receiving a flow mapping command, the ER allocating a bearer path for the user service stream based on the allocated resources, and transferring an execution result to the CA via the bearer control layer.