Abstract: The electrical properties of ABS resin filled with carbon fibers,mixed by solvent, two-roll mill and brabender were studied in this paper.The relationship between the fiber content and the resistivity of the composites was obtained and its conductive mechanism was analyzed.By comparing the results it was shown that the aspect ratio of carbon fibers plays an important role in the resistivity of the composites.Other factors such as fiber distribution in the composites also have some effects on it.Shielding effects of these composites were obtained by theoretical calculation.