The present invention discloses a policy control method and system, and a relevant apparatus. The method includes: receiving, by a policy decision apparatus, a control policy request sent by a gateway device, where the control policy request carries a subscriber identifier; sending, by the policy decision apparatus, a session request message carrying the subscriber identifier to a charging system; receiving, by the policy decision apparatus, a response message; receiving, by the policy decision apparatus, a notification message sent through an established session by the charging system, and generating a service data flow control policy according to information of an occurred charging relevant event; and sending, by the policy decision apparatus, the control policy to the gateway device. The method may implement, based on charging relevant information of a subscriber, policy control of a data flow, flexibility is desirable, and service experience of the subscriber is good.