This paper proposes a distributed network with master-slave structure and its synchronization scheme suitable for outdoor installation transformer protection, in which sub protection machines are configured with transformer breakers, transformer body sub machine is also used as the protection master, conventional sampling and tripping mode are adopted directly, and all of the external connections uses the prefabricated aviation plugs. The master transformer protection machine uses IEEE 1588 network synchronization protocol to realize the synchronous data sampling of each side sub protection machine, and with the data from other sub machines, the master protection machine achieves all of the protection functions and MMS communication. The master transformer protection machine sends out tripping GOOSE commands when the protection acts, and each side sub protection machine parses the receiving tripping command to cut the breaker of its side. This scheme allows all of the protection devices in the 110 kV and above voltage level substations to meet the requirements of outdoor installation, cancels protection's closet, and reduces the floor area of newly built substation. This work is supported by Science and Technology of Headquarters of State Grid Corporation of China (No. SGJSJX00YJJS1601932).