High level of expanded graphite (EG) was melt-blended with high-density polyethylene to prepare electrical conducting masterbatch. Some factors such as processing temperature, EG contents, treating time were discussed for the effect on electrical and mechanical properties of composites. Results showed that EG tends to reunite while the content of EG is higher than 60% because of the large aspect ratio and surface area of EG nanosheets. In addition, increasing processing temperature and mixing time appropriately could enhance the dispersion of EG, leading to improvement in electrical and mechanical properties. Scanning electron microscopy (SEM) measurements were used as an assistant analysis to study the microstructure of composites. (c) 2007 Wiley Periodicals, Inc.