This application provides a communication method, a network element, a terminal apparatus, and a system. The communication method includes: receiving, by a first network element, first indication information from a second network element, where the first indication information is used to indicate that a current condition supports establishment of a session of a first network for a terminal apparatus; obtaining, by the first network element, first quality of service QoS control information of a first session of the terminal apparatus after receiving the first indication information, where the first session is a session established by the terminal apparatus by using a second network; and sending, by the first network element, the first QoS control information to the second network element. The communication method in the embodiments of this application can improve communication efficiency.