Polypropylene/multi-walled carbon nanotube (PP/MWNT) nanocomposites were prepared in a twin screw extruder using masterbatch dilution technique. The nano-dispersion state of the nanotube in polymer matrix was estimated using rheological measurement, SEM and TEM. The effects of melt viscosity of PP and processing conditions such as screw speed and screw L/D ratio on the dispersion state and electrical property of the PP/MWNT nanocomposite were investigated. According to rheological and electrical properties, nanocomposite based on lower viscosity polypropylene has better performance compared to that based on the higher viscosity PP. As the screw speed increased the viscosity of PP/MWVT composite was increased but further increase in screw speed resulted in the decreased viscosity, which may be due to possible defects in MWNT. The mechanical properties of nanocomposites as increasing contents of MWNT were also investigated with the processing conditions.