A domain gateway control system and a method are provided. The system includes a gateway device configured at an interface of a domain. The gateway device is further linked to more than one Ethernet. When the gateway device analyzes a data packet acquired from an Ethernet and detects that a destination MAC address data of the data packet points to a net device in the domain, the gateway device records a gateway MAC address data in a source MAC field of the data packet and records a domain type code data corresponding to the domain in an Ethernet-type field of the data packet to convert the data packet into a domain packet used in the domain. Any net device in the domain that acquires the domain packet learns the gateway MAC address data, and does not learn a device MAC address data of an external device of the Ethernet.