Wet-type jet milling (WJM) was used as a pre-treatment procedure for carbon nanotube (CNT) which was utilized as electrical conductive filler for polymer nanocomposites. Nanocomposites were prepared by dispersing WJM treated CNT (WJM-CNT) or as-received CNT (AR-CNT) in isotactic polypropylene matrix, and the effect of WJM pre-treatment on nanocomposite properties was investigated. Dispersion structure of CNT was observed by SEM and electrical property was studied by impedance spectroscopy. DC conductivities (sigma(DC)) showed different CNT concentration dependences, which were characterized by the percolation critical exponents. At 0.5 wt% of CNT, sigma(DC) increased two-fold by using WJM-CNT. Analysis of imaginary part of impedance spectra and complex dielectric permittivity suggested the WJM-CNT nanocomposites had much complicated local structure as compared to the AR-CNT counterparts. These electrical properties were discussed in relation to the dispersion structure of CNT. (C) 2014 Elsevier B.V. All rights reserved.