The role of KOH in the one-stage KOH-activation of rice straws was studied using FTIR, XPS, TGA, and DTG techniques.It was found that at the impregnation, KOH extracts to some extent the lignin component from rice straw and reacts withhydroxyl groups. On heat-treatment, the impregnated KOH facilitates intermolecular condensation reaction on one hand butretards the thermal degradation of cellulose molecules on the other hand. The oxygen-containing surface functional groupsnewly created by oxidation of KOH may facilitate the bulk, not controlled, consumption of carbon atoms so that the effectiveporosities may not be able to be developed by the one-stage activation process.