A method for preparing porous fabrics is disclosed. The method includes transporting PAN-based oxidized fabrics to a thermal treatment chamber, which provides multi-pipe to introduce oxygenated gas and oxygenated fluid respectively, by using a plurality set of rollers to carry out an activation-carbonization process. The activation-carbonization process is preformed within a temperature range of 1010° C. to 1500° C., and produced the porous activated carbon fabrics that provide uniform nano-pore with BET surface area about 800˜1500 m2/g.