Disclosed are a session association method, device and system. The method includes: a PCRF or BPCF receiving a first session from a fixed network, wherein the first session carries an IP address and port number set; the PCRF or BPCF receiving a second session from an AF or traffic detection function (TDF), wherein the second session carries an IP address and port number information; and the PCRF or BPCF associating the first session and the second session according to the IP address and port number information. The present invention solves the problem of inaccurate session association in the scenario where a mobile terminal directly accesses mobile network services via a fixed network.
