Activated carbon hollow fiber (ACHF) was prepared from polyacrylonitrile (PAN) hollow fiber through carbonization in nitrogen and activation with carbon dioxide. The effect of the activation time on the pore size distribution and the surface structure of the resulted ACHF was investigated. The results show that increasing the activation time at 800 degrees C can increase the number of pores and reduce the crystal size, the tensile strength, the modulus, and the elongation.