Aniline-modified multi-walled carbon nanotubes (MWNT) have been obtained through interaction between carboxylated MWNT and aniline in aqueous solution. The influence of three species carboxylation treatment on the interaction has been studied. FT-IR spectra bands detectable in this case implied the generation of amide bonds and the conjugation of aromatic ring in samples. The results show that citric acid serves as super intermediate medium in the course of aniline-modified MWNT. Moreover, higher temperature can promote the modified procedure significantly.