A decision-making method, a decision-making system, and a PDF are disclosed herein. The decision-making method comprises: receiving application session data that carries access network data and access user data; and making policy and charging decisions according to the application session data. Through the decision-making method, decision-making system, and PDF, the application session data comprises access network data and access user data of the UE so that the PCRF can uniquely determine a user according to the access network data or the access user data and the IP address allocated by the network to the UE, and make policy and charging decisions.