A method and a system for exercising policy control, a policy and charging enforcement function (PCEF) are provided, which can solve the problem that no policy control can be exercised over application service flows without an application function (AF). In the method, a PCRF receives information about an application event sent by a PCEF after subscribing the application event from the PCEF; and the PCRF generates a control policy for a service flow of the application according to the information about the application event. In the present invention, the PCEF sends the obtained information about the application event to the PCRF, so that even when no AF is involved, the PCRF can still generate a control policy according to policy contexts including the information about the application event and the like.