Porous structure and surface chemistry of activated carbon fibers obtained by different precursors and activation methods were investigated. Adsorption isotherms were characterized by nitrogen adsorption at 77K over a relative pressure range from 10~(-6) to 1. The regularization method according to Density Functional Theory (DFT) was employed to calculate the pore size distribution in the samples. Their specific surface areas were calculated by BET method, micro pore volume and micro porous specific surface area calculated by t-plot method and MPD by Horvath-Kawazoe equation. Micropore volume of rayon-based ACF was higher than that of other samples. The static and dynamic adsorption capacity for formaldehyde on different ACFs was determined. The results show that steam activated Rayon-based ACFs had higher adsorption capacity than that of steam and KOH activated PAN-ACFs. Breakthrough curves illustrated that Rayon-ACFs had longer breakthrough time, thus they possessed higher adsorption capacity for formaldehyde than that of PAN-A CFs. The entire sample had small adsorption capacity and short breakthrough time for water. Rayon-ACFs had excellent adsorption selectivity for formaldehyde than PAN-ACFs. And the samples with high surface areas had relatively high adsorption capacity for formaldehyde. Elemental content of different ACFs were performed. Rayon-based ACFs contained mare oxygen than PAN-ACFs, which may be attributed to their excellent adsorption capacity for formaldehyde. Porous structure and surface chemistry of activated carbon fibers obtained by different precursors and activation methods were investigated. Adsorption isotherms were characterized by nitrogen adsorption at 77K over a relative pressure range from 10-6 (-6) to 1. The regularization method according to Density Functional Their specific surface areas were calculated by BET method, micro pore volume and micro porous specific surface area calculated by t-plot method and MPD by Horvath-Kawazoe equation. Micropore volume of rayon-based ACF was higher than that of other samples. The static and dynamic adsorption capacity for formaldehyde on different ACFs was determined. The results show that steam activated Rayon-based ACFs had higher adsorption capacity than that of steam and KOH activated PAN -ACFs. Breakthrough curves illustrated that Rayon-ACFs had longer breakthrough time, thus they possessed higher adsorption capacity for formaldehyde than that of PAN-A CFs. The entire sample had small adsorption capacity and short breakthrough time for water. Rayon-ACFs had excellent adsorption selectivity for formaldehyde than PAN-ACFs. And the samples with high surface areas had relatively high adsorption Capacity for formaldehyde. Rayon-based ACFs contained mare oxygen than PAN-ACFs, which may be attributed to their excellent adsorption capacity for formaldehyde.