The preparation method and performance test of Carbon Nanometer Tool(CNT) electrodes were explored on the basis of a nanometer test system. Firstly, a CNT electrode was prepared by voltage arc discharge. Then, the volt-ampere characteristic of the CNT electrode was measured online to analyze the resistance variation of CNT and the tungsten needle before and after welding. Finally, the contact characteristic between CNT and tungsten needle was improved by local Joule heating, the resistance of CNT electrode was reduced by Au sputtering, so that the holistic conductive performance of CNT electrode was improved greatly. Experimental results indicate that the resistance of CNT electrode is about 130 kΩ, which is much fewer than the sum resistances of CNT and tungsten needle before welding. The resistance of CNT electrode is reduced to 55 kΩ after 90 s local Joule heating, which is 60% lower than its initial resistance and improves the contact characteristic between CNT and tungsten needle obviously. Moreover, the resistance of CNT electrode is reduced to 40 kΩ after Au sputtering, which is 70% lower than its initial resistance and, improves its conductive performance effectively.