Pretrea tments of the visco serayon based activ ated carbon fibers (ACFs) with acid (HNO3, H2 SO4, HCl), a lkali (NaOH) and steam were carried out to modify the surface characters of ACFs. The activ it ies of ACFs for selective cataly tic reduction (SCR) at lower temperature were tested. There is an increase in the content of functional group with oxygen on the surface of ACF and a decrease in micropore range for the ACF treated with HNO3. The new functional groups are form ed for the ACF treated with H2 SO4, HC l and NaOH, which can improve the activity of SCR, and an increa seinm icropore range forACF treated with NaOH is found. How ever, the portion of mesopores increases but the cataly ticactivity of ACF decreases for the ACF treated with steam.