This patent application provides a multi-connectivity data reporting method, including: obtaining, by a first network device, a first data volume report, where the first data volume report is used to indicate a volume of data that are of a terminal device and that pass through a second network device; and sending, by the first network device, the first data volume report to a third network device. The first data volume report includes one or more of QoS flow identifiers (QFIs) of one or more quality of service QoS flows, identifiers of one or more protocol data unit (PDU) sessions to which the one or more QoS flows belong, or data volumes of the one or more QoS flows.