The present invention provides an intelligent electric energy meter RS485 communication interface fault self-detection isolation device, comprising an A port and a B port connected to a collecting terminal and a contact point, an A' port and a B' port connected to the electric energy meter, and a voltage stabilizing circuit and a port undervoltage control breaking circuit disposed between ports, wherein, the voltage stabilizing circuit is symmetrically disposed between the AA' port and the BB' port for stabilizing an RS485 communication interface voltage, and the port undervoltage control breaking circuit comprises a first photosensitive diode, a second photosensitive diode and a first light emitting diode, the first photosensitive diode is disposed on an AA' port line, the second photosensitive diode is disposed on a BB' port line, and the first light emitting diode is disposed between the A'B' ports and is encapsulated in a cassette together with the first photosensitive diode and the second photosensitive diode, the first light emitting diode is configured to emit driving light when a voltage between A'B' is normal, to drive the first photosensitive diode and the second photosensitive diode to be conducted.