In this paper, the effect of the temperature of steam activation on textural properties of coal tar pitch-based activated carbon fibers (ACFs) was studied. Surface properties of the ACFs were determined by using scanning electron microscope (SEM) and X-ray diffraction (XRD). $N_2$ adsorption isotherms at 77 K were investigated by BET and BJH methods to characterize specific surface areas, pore volumes, and pore size distributions. The adsorption isotherms of the ACFs were constructed and analyzed to be of Type I, mainly consisting of micropores. The specific surface areas of the ACFs were increased with activation time and showed a maximum value of $2442m^2/g$ at an activation temperature and time of $900^{circ}C$ and 40 min, respectively.