In this paper, we attempted to narrow the pore size of Pitch-based activated carbon fiber (Pitch-ACF) by chemical vapor deposition (CVD) of propylene at 700 degrees C. The BET equation was used to estimate the specific surface areas. The micropore volumes were determined using DR equation, t-plot and alpha(S)-plot, and mesopore surface areas were determined by t-plot and alpha(s)-plot. The pore size distribution (PSD) of micropores and mesopore was investigated by micropore analysis method (MP method) and MK method, respectively. The relation between the graphite-like crystal interlayer distance and pore size was analyzed by X-ray diffraction (XRD). The results showed that the pore size of Pitch-ACF was gradually narrowed with increasing deposition time. The catalytic activation of Ni was attempted when Pitch-ACF was modified simultaneously by pyrolysis of propylene. The results obtained from the analysis of PSD of micropores, mesopores, and macropores in Ni-P-ACF by density function theory (DFT) showed that the pore structure and surface chemistry were greatly changed due to introducing nickel catalyst. (c) 2004 Elsevier B.V. All rights reserved.