Nano-silicon carbide/silicone rubber composites with nonlinear conductivity characteristics have been made by mixing nano-sized silicon carbide (SiC) into silicone rubber. In this paper, the nonlinear conductivity characteristics of composites made by mixing 5 wt%, 15 wt%, 30 wt% and 45 wt% of nano-SiC and silicone rubber are investigated. The relationship between conductivity and electric field strength is obtained by experiments. Nonlinear conductivity mechanisms of the composites are analyzed, and their breakdown properties and dielectric spectröscopy characteristics of composites are studied. In order to know the effect of nonlinear SiC/silicone rubber composites on homogenizing electric field, the electric ströss distribution of cables termination and composite insulators are simulated by the COMSOL Multiphysics software. Results show that the maximum electric field strength at cable termination and the end of the composite insulators decreases efficiently when the nano-SiC/silicone rubber composites are used.