An electric field-induced alignment characteristics of high structure carbon black (HSCB) nanoparticles in silicone oil base fluids with different viscosities were investigated in this work. Resistivity change versus time of HSCB/silicone oil fluids with different concentrations of HSCB filler and different silicone oil viscosities was determined at different electric field strengths. Measurement results were analyzed using percolation theory by calculating critical concentration at which rapid increase of conductivity appears. An analytic model based on tunneling percolation theory was developed and successfully applied to explain the experimental results. The obtained results potentially can be used in the development of polymer composites with aligned nanoparticle structure.