Halloysite nanotubes decorated with self-assembled protonic acids monolayer (SPAM-HNTs) was successfully prepared by anchoring the organic sulfonic acid onto the surface of tubular halloysite, and performed as in situ dopant to obtain the conducting SPAM-HNTs/PANI nanocomposites via in situ chemical oxidative polymerization of aniline. The surface functionalization of HNTs with protonic acids monolayer was found to play an important role in the formation of the well-defined coaxial tubular structure as well as the high doping degree of PANI. Moreover, the thermal stability of the SPAM-HNTs/PANI nanocomposite was clearly enhanced, and the SPAM-HNTs/PANI nanocomposite was possessed of good conductivity in magnitude up to 10(-1) S/cm at room temperature without any other external additives. The effect of the SPAM-HNTs feeding ratio on the electrical conductivity of the products was also emphasized. (C) 2012 Elsevier Ltd. All rights reserved.