A novel actuating single wall carbon nanotube (SWNT)/polymer composite is reported. It exhibits a large strain (2.6%) at a low driving voltage (<1 MV m(-1)) while possessing excellent mechanical and thermal properties. The strain energy density is at least an order of magnitude greater than any state-of-the-art polymeric materials eported. The actuating characteristic rmainly originates from the electrostrictive contribution, presumably due to interfacial polarization.