TiO2-containing pitch fibers were prepared and various stabilization variables were investigated by characterizations of the fibers and behaviors of TiO2 particles in the optimum stabilization conditions. When pitch fiber was stabilized by air at the optimum condition, the fiber weight increased as an increase of the stabilization temperature and a decrease of TiO2 concentration. The carbonization yield was 71~82 wt.%, showing a decrease of the yield with the TiO2 increase caused by the catalytic activity of TiO2 to combustion. During the stabilization, newly developed carbonyl and carboxyl groups were introduced on the fiber surface and cross-linking reactions were progressed resulting the thermosetting property, which was verified by the replacement of hydrogen with oxygen. Pore size of the activated carbon fiber was increased by an increase in TiO2 concentration. In the considerations of the aggregation behaviors of the TiO2 particles, the optimum stabilization conditions of 0.5 wt.% TiO2 containing petroleum-based pitch fiber were suggested as 280 ℃, 3 hr.