In this study, LDPE was used as the polymer matrix. LDPE/graphene NCs with the filler content of 0, 0.005, 0.01, 0.1 and 0.5 wt% are prepared. The breakdown strength, conductivity, space charge behavior, and trap level distribution of the NC were measured. According these results, a schematic model is proposed to illustrate that charge carrier transport process modulated by trap, which further reveals the relationship between electrical properties and trap energy level distribution.