Carbon nanotubes/polyacrylic acid coating materials have been synthesized by in situ precipitation polymerization. The coating structure of functionalized CNTs was characterized by infrared spectrometer, thermogravimetric analyzer, and transmission electron microscopy. The results showed that PAA has coated on the surface of CNTs. The polyacrylic acid-functionalized CNTs could be dispersed in water, then forming stable dispersions. The amount of PAA grafted was dependent on CNTs/monomer ratios.