A new species, Grimmia grevenii C. Feng, X.L. Bai & J. Kou, endemic to the Wudalianchi volcanoes in the province of Heilongjiang in northeast China, is described and illustrated. It is characterized by low, white-hoary cushions, ovate-lanceolate leaves clearly contracted to the base and with rounded apex, both margins slightly recurved at the base but otherwise plane, basal and upper laminal cells not obviously differentiated, basal areolation nearly uniform, costa markedly broadened at insertion, not at all projecting on abaxial side. The new species is contrasted with two most similar species in the genus, G. maido H.C. Greven and G. longirostris Hook.