Abstract: Carbon black (CB) was oxidized by HNO3 and the surface oxygen content (molar ratio of oxygen to carbon) of CB increased from 1.0%(CB1) to 7.0%(CB2). Using CB1 and CB2 as fillers, highdensity polyethylene(HDPE) as matrix, two conductive composites were prepared. With higher surface oxygen content of CB, the percolation threshold of filled HDPE composites was lower, which was on contrary to that of carbon particles filled polar polymer composites of CB2. The dispersion and agglomeration behaviors of CB1 and CB2 in HDPE were analyzed by scanning electron micrography, dynamic percolation effect and Payne effect. Results showed that CB2 particles dispersed more unevenly and agglomerated to form conductive networks more easily in HDPE matrix. The ability of CB agglomerate to form conductive networks in HDPE melt increased with the increasing of the surface oxygen content of CB particles.