The high-density polyethylene (HDPE) conductive composites filled separately with carbon fibers (CFs), ethylene-vinyl acetate copolymer (EVA), and three kinds of carbon blacks (CBs) (including different diameter, BET specific area, and DBP value) were prepared, to investigate the influence of the property, size, and content of the conductive fillers on the nonlinear voltage?current characteristics of the HDPE conductive composites. The results showed that the relationship between the electric current density and the electric field intensity of the three HDPE/CB composites including the HDPE/CF composites, the HDPE/CB/CF composites, and the HDPE/EVA/CB composites was nonlinear. The nonlinear conductivity index of the HDPE/CF composites was kept a low level comparing to the HDPE/CB composites, the HDPE/CB/CF composites, and the HDPE/EVA/CB composites. Moreover, the nonlinear conductive behavior mechanisms were discussed.