The present invention discloses a long-reach Ethernet system. The system includes a first Ethernet device and a second Ethernet device which communicate with each other, and a relay; wherein one of the first Ethernet device and the second Ethernet device is a conventional Ethernet device, and the other one of the first Ethernet device and the second Ethernet device is a conventional Ethernet device or a long-reach Ethernet device; the first Ethernet device and the second Ethernet device communicate with each other via the relay; and the relay is adapted to transform conventional Ethernet data into long-reach Ethernet data and transform long-reach Ethernet data into Ethernet data. The present invention can realize the communication of two Ethernet devices when at least one of the two Ethernet devices is a conventional Ethernet device and a working distance between them is longer than 100 meters.