We studied the surface modification of polyimide/multi-walled carbon nanotube (MWNT) composites resulting from plasma treatment. After NH₃ plasma treatment, the surface properties of polyimide containing MWNT (U-CNT) or acid modified MWNTs (M-CNTs) were investigated using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), contact angle and electrical measurements. The surface of polyimide/MWNT composites became more hydrophilic after the NH₃ plasma treatment, which improved the surface electrical conductivity of polyimide/MWNT composites. The XRD results indicate that the formation of a MWNT network structure in the polyimide matrix impeded the motion of polyimide molecules.