The KOH-activated mechanism of graphene is mainly accorded to that of ACs; however, the chemical composition of graphene and AC precursor is different. In order to reveal the mechanism of KOH-activated graphene and controllably prepare the desired activated graphene, our group systematically studied the nature of graphene in the porosity development of activated graphene. It was found that the active sites (non-sp2 hybrid carbon, including defective place and carbon attached with oxygen-functional groups) play an important role in the activation process. The precursor graphene with low crystallinity and high content of double-bond oxygen functional group is ideal for producing highly porous activated graphene.