Embodiments of this application relate to a method for controlling service flow transmission. One example method includes: a session management network element obtains a first TMBR of a service flow transmitted in a session by using a first access technology and a guaranteed bandwidth of a first GBR service flow, where the TMBR indicates a TMBR of service flows transmitted in the session by using the first access technology. The session management network element sends first information to a data plane network element, where the first information is used by the data plane network element to determine one or more of the following information of the session: a first AMBR, a second AMBR corresponding to the first access technology, and a second TMBR. A second AMBR indicates an AMBR of a non-GBR service flow transmitted in the session by using the first access technology.