A new approach, mild blending method, to prepare carbon black (CB) filled polypropylene (PP) nano-composite using CB aqueous suspension was reported in this study. In this compounding process, the CB particles were first dispersed in aqueous suspension by using an ultrasonic irradiation. Subsequently, the CB suspension was blended with melting PP using an extruder with low shear strength screw configuration, followed by removing the vapor from the vent by vacuum. The morphological observation showed that the CB particles were dispersed at a nanometer level in the nanocomposites as they were in aqueous suspension and distributed homogeneously in PP matrix. The CB/PP nanocomposite prepared by this method exhibited a very low percolation threshold, i.e., 2.49 vol %, and a high-critical resistance exponent t (t = 5.82). These phenomena, which deviated from the classical percolation theory, were likely to come down to the homogeneous distribution of CB particles and the tunneling conduction. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 115: 2629-2634, 2010