In this paper, impregnated activated carbon fiber (IACF) was manufactured to pitch-based activated carbon fibers (ACF) with potassium hydroxide (KOH) by using wet impregnation method to raise nitrogen oxides (NOx) adsorptivity. The properties of IACF were observed using EPMA, TGA and DSC and NOx adsorptivity was observed at high and low temperature. Before and after adsorption was analyzed using ToF-SIMS for examine surface characterization of adsorbed NOx. The results showed that the better adsorptivity appeared for increasing KOH ratio. So, NOx adsorptivity showed result that is proportional between KOH and the adsorbed amount. On the other hand, adsorbent that manufactured without washing was better NOx adsorptivity than adsorbent that manufactured with washing. The behavior of adsorption show that crossing time of NO and NO2 delayed for a rising adsorptivity. And NO ratio increased but NO2 ratio decreased according as KOH ratio increases. NOx was confirmed through surface analysis that remain in NO2- and NO3- form on IACF surface.