Abstract: Polyimide/carboxylated multiple-walled carbon nanotubes（PI/MWNTs-COOH） nanocomposites were synthesized by in situ polymerization using 4,4’-oxydianilline（ODA）,pyromellitic dianhydride（PMDA） and MWNTs-COOH which was prepared by microwave-assisted oxidation.Raman,FT-IR spectroscopy and TEM images confirmed that the surfaces of the functionalized MWNTs possessed the polar groups of carboxyl and hydroxyl groups.A homogeneous disperson of MWNTs-COOH was achieved in polyimide matrix as evidenced by SEM characterizations,while the structure of the polymide and multiple-walled carbon nanotubes was stable in the preparation process demonstrated by FT-IR and XRD spectroscopy.According to the DMA,DSC and TGA analysis,the resultant PI/MWNTs-COOH nanocomposites both exhibit excellent thermal resistance,and have stronger thermal stability than pure polyimide due to the strong interfacial interaction between the MWNTs-COOH and polyimide matrix,which is favorable for practical use in heat-resisting material.