The neglected genus to the floras of Kinmen and Matsu, Cleistogenes Keng (Poaceae), and its species, C. hackelii (Honda) Honda, was described and illustrated in this article. Populations of this neglected and new-recorded grass species distributes in temperate and subtropical regions of East and Northeast Asia, and its subpopulations in the Kinmen island and Matsu archipelago locate on sunny coastal grasslands and forest floors.