（Mn7C3, Ni）@C nanoparticles were synthesized for electrode material in a supercapacitor. Using DC arc-discharge method, in which the anodic target of Ni-Mn mixture was evaporated in the methane atmosphere by a tungsten cathode. The prepared nanoparticles own a well-defined core/shell structure with average diameter of 50 nm. Encapsulated inside of the carbon shell, the core of the nanoparticles is composed of Mn7C3 and Ni. Owing to its catalytic effect, Ni promotes the growth of carbon shell which has the typical double-layer capacitance. Meanwhile MnTC3 as the product of Mn-C reaction is able to provide pseudo-capacitance. The proportion of Ni-Mn in the nanoparticles consequently affects the overall electrochemical performance of the electrodes. The specific capacitance of the elec- trode increases with the promotion of Mn content （485.12 F/g）. The results shows that the nanoparticles with more Ni have better cycle stability （303.57 F/g） and retain 70% of the initial capacitance after 1000 cycles.