Poly(p-styenesulfonate acid)-grafted multi-walled carbon nanotubes (PSSA-g-MWCNTs) were prepared by in situ polymerization of sodium p-styrenesulfonate in the presence of MWCNTs, followed by refluxing with concentrated hydrochloric acid. In this reaction system, sodium p-styrenesulfonate served not only as the reaction monomer but also as an amphiphilic dispersant to disperse pristine MWCNTs in water, which is critical for the grafting PSSA onto MWCNTs. Due to the existence of copious sulfonic groups (-SO3H), PSSA-g-MWCNTs could be stably dispersed in polar solvents, such as water and methanol. This is favorable to the application of PSSA-g-MWCNTs as a solid-acid catalyst in a heterogeneous catalytic reaction. The PSSA-g-MWCNTs showed high catalytic activity in the esterification of lauric acid with methanol, and could be easily separated from the product by filtration. The catalytic activity of PSSA-g-MWCNTs showed no detectable change even after recycling after being used for three times. Crown Copyright (C) 2010 Published by Elsevier BM. All rights reserved.