In this article, the volume conductivity of polypropylene (PP)/polyaniline (PANI)/multiwalled carbon nanotube (MWNT) composites was detected. When the ratio of PANI protonated with dodecylbenzene sulphonic acid (PANI-DBSA) to MWNT is 2 to 3 and 3 to 17, the volume conductivity of the two composites is much higher than that of composites filled with solely PANI-DBSA or MWNT. The synergistic effects of PANI-DBSA and MWNT on the microstructure and the electric property of PP/PANI/MWNT composites were carefully analyzed by scanning electron microscope (SEM) and transmission electron microscopy. The SEM results illuminate that the dispersion and the continuity of the composites filled with PANI-DBSA and MWNT are far better than that filled with only PANI-DBSA or MWNT. Especially, the dispersion and continuity of PP/PANI/MWNT 5, in which the ratio of PANI-DBSA to MWNT is 3 to 17, are the best among all the composites. When PANI-DBSA is introduced in PP/PANI/MWNT composites, the size of agglomerated particles decreases, and the dispersion of conductive particles is improved evidently. Therefore, there is a synergistic action of PANI-DBSA and MWNT, which is used to improve the dispersion of conductive particles and the volume conductivity of the PP/PANI/MWNT composites. POLYM. ENG. SCI., 2012. (C) 2011 Society of Plastics Engineers