To improve the integrated accuracy of high-voltage power metering system， a type of all-digital power metering system is developed based on the high-voltage electronic instrument transformers. Compared with the conventional approach， the signal transmission media of this new type of power metering system is changed from copper cable to fiber， and the metering instrument from the 5 A/110 V analogue input device to a device with a digital input interface. A performance analysis is made of the comparison between the proposed system and the conventional one， and the benefits of the new approach are described. The realization of the proposed power metering system on a 35 kV voltage grade power system is described.