A differentiated service (DS) domain generating method, a device, and a system. A network management device obtains device attribute information of multiple DS devices; determines according to the device attribute information of the multiple DS devices, a DS device that belongs to a first DS domain; and sends a notification message to the DS device that belongs to the first DS domain, so that the DS device that belongs to the first DS domain joins the first DS domain according to the notification message, thereby implementing automatic determining and generation of a DS domain, reducing workload of configuring quality of service (QoS) parameters in a DS domain including a relatively large number of devices, and improving efficiency in generating and maintaining the DS domain.