To prevent parallel device damage and breaker tripping fault occur caused by PT parallel reverse charge, a PT parallel device based on ARM is developed, which has fault location function and can prevent reverse charge. This paper introduces the device’s working principle and the overall structure, hardware and software design in detail. The device takes data acquisition and calculating of in-phase voltage difference as parallel necessary condition, and has the advantage of preventing abnormal parallel and reverse charging function compared to traditional PT parallel device. In parallel circuit, it designs an overcurrent blocking circuit based on new electric component PPTC, with transient fault isolation and automatic recovery function. By the voltage comparison and discrimination, it can identify the high voltage fuse breaking, breaking tripping, and bus ground fault automatically, which has the function of fault location. It also can real-time display each phase voltage and fault information, which greatly shortens the maintenance personnel troubleshooting time and enhances the safety and stability operation of the power supply.