Multi walled carbon nanotubes (MCNT) synthesized by CVD method have been successfully cut into different lengths by controlling HSO4/HNO3 (5:3) oxidation time. During the cutting process H2SO4 and HNO3 were added independently and the oxidation processes were carried out at a lower temperature to void excess weight loss and damage to MCNT. The resulting shorted MCNT (s-MCNT) formed stable dispersion state in the polar solvents without the help of surfactants that provided possibility for further functionalization and application. Moreover, NaOH solution was used to determine the total percentage of acidic sites and the total percentage of acidic sites are about 0.2-1%. (c) 2005 Elsevier B.V. All rights reserved.