The influences of processing conditions on polyethylene/carbon black composites with two types of PE are studies in this paper, including mixing temperature, mixing time, additives, heating treatment and irradiation. And the optimized process conditions are obtained. It is found that the composites based on different PE matrices exhibit different properties, which is attributed to the different viscosity of the matrices. PE20/CB composites show excellent mixing properties, low room —temperature resistivity and considerable PTC effect when containing 18%—26% content of CB, while PE2/CB composites are much better in stability and the elimination of NTC effect. It is suggested that the combination of different matrices in one composite may be a convenient method to fabricate more superior polymeric PTC materials.