The utility model discloses an automation three-layer-protection system of a distribution network. The system includes a power-distribution master station, power-distribution sub-stations, power-distribution remote terminals and a communication channel. The power-distribution master station, the power-distribution sub-stations and the power-distribution remote terminals are all connected to the communication channel. The power-distribution master station is provided with a distribution-network control host. The power-distribution sub-stations are provided with power-distribution control extension sets. The distribution-network control host and the distribution-network control extension sets are connected to the communication channel. The power-distribution sub-stations are arranged in a transformer substation. Each power-distribution remote terminal includes a power-distribution terminal device and a ring-main-unit terminal device, both of which are connected electrically with a power-distribution switch. The power-distribution switches are arranged on a power-distribution line which is connected from a transformer of the transformer substation to UE. The automation three-layer-protection system of the distribution network realizes three-layer protection of a distribution network system through the power-distribution master station, the power-distribution sub-stations and the power-distribution remote terminals so that the system is high in reliability, high in fault-point judgment speed and isolation speed and lowered in demands of topology relevancy of the distribution network system and the power-distribution switches.