Aiming at a novel adsorption agent material, ACF/CNT composites were fabricated by growing carbon nanotubes (CNTs) on the surface of activated carbon fibers (ACFs) with chemical vapor deposition (CVD) method. The characteristics of ACF/CNT composites were investigated by SEM. The variables effects on CNTs size, uniformity and density were evaluated. Three major variables were optimized as the concentration of catalyst precursor 0.07 mol/L, pyrolysis temperature 750 and pyrolysis time 40 min respectively. The results show that CNTs are uniform distribution on the surface of ACFs and the diameter of CNTs is in the range of 30-60 nm and BET specific surface area is 65.39 m2/g. ACF/CNT composites are looked forward to be a promising materials for wastewater and flue gas treatment and hydrogen storage for proton exchange membrane fuel cells.