In order to study the effect of introducing ethylene-ethylacrylate copolymer (EEA) in carbon black-HDPE composite systems, two HDPE-EEA composites prepared by pre-blending and masterbatch-blending processes were compared with HDPE and EEA composites in terms of positive temperature coefficient (PTC) characteristics and percolation threshold. The percolation threshold of masterbatch-blended composites occurred at the lowest carbon black concentration among four kinds of composites. The conduction path in the masterbatch-blended composite is effectively formed as a result of the localization of carbon black distribution predominantly in the EEA phase, resulting in an increase of conductivity. Ipeak values, the resistivity ratio of the peak to 25°C, of two blend composites were lower than those of HDPE composites. The I85 values, the resistivity ratio of 85°C to 25°C, of masterbatch-blended composites were higher than those of pre-blended as well as HDPE composites. It is evident that since most carbon black is dispersed in the EEA phase of the masterbatch-blended composites, the conduction networks are mainly broken by the crystal melting of EEA before the temperature reaches the crystal melting temperature of HDPE.