With the VEG model of electric vehicles been proposed, the large power off-board charge has been widely used owing to its safe and fast charging features. The 300kW verification system is figured out to cover full range calibration of large power vehicle charger in real-load, which uses six 50kW linear electronic load boxes joint substitution for capacity battery. And the DC voltage dividers and comparators will synchronously measure the voltage, the current, the error of electric energy and the price based on watt-second method in fielding calibrator. The verification system is provided the foundation for energy metering traceability for off-board charger. Finally, through the contrast and statistical analysis, the proposal that energy metrology unit should be placed in charger DC side had been put forward to achieve a fair settlement.