An investigation of the blend of PA66 / organic modified multi-wall carbon nanotubes (MWNT) is reported. The MWNT was carboxylated in a sulfuric and nitric mixed acid under ultrasonic vibration. In fact, the electrical conductivity of these composites is analyzed. The MWNT-filled PA66 shows percolation point of the electrical conductivity at low filler loadings (0.5-12wt%). Presumably, the carboxylated MWNT was reacted with PA66. The neat MWNT, carboxlyated MWNT, and PA66/MWNT composites were characterized with FTIR, polarity, DSC, and electrical conductivity.