Abstract: This paper proposes a design scheme for an intelligent operation and maintenance fault diagnosis device applied to low-voltage cable branch boxes. The device consists of a cable branch box fault detection host, supporting current sensors, voltage sensors, App software, and other components. It can monitor the operating conditions of the cable branch box in real time and identify typical outlet faults of the cable branch box. The device has various Internet of Things communication capabilities and can communicate with remote online monitoring platforms. The practical device developed based on this scheme has been applied in engineering practice and has shown good application results.