Embodiments of the present disclosure disclose a BUM traffic control method, a related apparatus, and a system. A traffic controller receives, through a tunnel, a BUM packet encapsulated by a network device in a target broadcast domain. The traffic controller collects, based on the received BUM packet, statistics about a BUM traffic value of a target object within a preset time period, and determines whether the BUM traffic value is greater than a preset BUM traffic threshold of the target object. If the BUM traffic value is greater than the preset BUM traffic threshold, the traffic controller controls BUM traffic of the target object, to reduce the BUM traffic of the target object. The foregoing solution can resolve a problem of BUM packet flooding caused by an increase in a quantity of hosts or an increase in a quantity of network devices in a communications network.