Abstract: Polypyrrole (PPy) filled with carboxylated multi-walled carbon nanotubes (MWCNTs),MWCNTs/PPy electrical conductive composites,were prepared via in-situ polymerization using pyrrole monomer and MWCNTs as raw materials.The structure and properties of composites were characterized by means of Fourier transformed infrared spectroscopy (FITR),scanning electron microscopy (SEM),thermogravimetric analysis (TGA) and four probes conductivity testing.The result show that the large surface area and high aspect ratio of carboxylated MWCNTs made a noticeable improvement in electrical conductivity and thermal stability of the prepared composites compared with pure PPys.The conductivity and thermal stability of MWCNTs/PPy composites increased with a increase of MWCNTs content,when the MWCNTs content was 20 wt%,it reached 11.1 S·cm-1.