Gra./Cu composites and CNTs/Cu composites were prepared by powder metallurgy. Chopping current and cathode spot movements of the 2 kinds of Cu matrix composites in vacuum were investigated. The results show that the vacuum arc of CNTs/Cu is more stable and dispersive, and the chopping current is less than that of Gra./Cu. For CNTs/Cu the size of cathode spot craters is 0.1-5 μm in diameter, while for Gra./Cu is between 10 and 100 μm. The common characteristics are that cathode spot initiates selectively on the Cu phases and walks randomly on the surface of the Cu matrix composites. It is concluded that CNTs/Cu has an higher arc erosion resistance than Gra./Cu, and CNTs can effectively increase stability and lower chopping current of the Cu matrix composites.