Multi-walled carbon nanotube (MWCNT) modified by vinyltriethoxysilane (VTES) via free radical reaction has been prepared (poly (vinyltriethoxysilane) modified MWCNTs, PVTES-MWCNT). Precursor of polyimide, polyamic acid has been synthesized by reacting 4,4'-oxydianiline with 3,3',4,4'-benzophenone tetracarboxylic dianhydride. PVTES-MWCNT were then mixed with polyamic acid and heated to 300 degrees C to form CNT/polyimide composite. During the imidization processes, the silanes on CNT surface reacted with each other and may be connected together by covalent bond (Si-O-Si). The PVTES-MWCNT was analyzed by Fourier transform infrared and X-ray photoelectron spectroscopy. The PVTES-MWCNT/polyimide composites were analyzed by CP/MAS solid state Si-29 nuclear magnetic resonance (NMR) spectroscopy. Morphological properties of the PVTES-MWCNT/polyimide composites were investigated by scanning electron microscope and transmission electron microscope. Electrical conductivity increased dramatically comparing to the unmodified MWCNT/polyimide composites. Mechanical properties of nanocomposite were enhanced significantly by PVTES-MWCNT. (C) 2007 Wiley Periodicals, Inc.