Currently, the number of on-site installation acquisition terminals and energy meters in the power system is very large. Because of the complexity of the environment, result in more on-site measurement of failure to field operation and maintenance personnel a great deal of pressure, there is an urgent need for fast, automated troubleshooting and fault diagnosis of the metering device. However, at present the domestic market has not specifically for the measurement of field fault detection device. And on-line monitoring fault diagnosis system reported in the literature, can only diagnose the communication of the metering device, which is difficult to meet the actual needs. This paper proposes a portable fault site investigation and diagnosis device for energy metering equipment. The proposed device can be applied to the field of energy metering equipment maintenance, which is proved by our experiments.