Grimmia caotongiana D. P. Zhao, S. Mamtimin & S. He, a new species of Grimmiaceae from Xinjiang Uyghur Autonomous Region of China, is described and illustrated here. The new species is most similar to Grimmia anodon Bruch & Schimp., but is distinguished by the absence of hair points in both vegetative and perichaetial leaves, the leaf margins narrowly recurved at middle and lower part, and the basal juxtacostal cells mostly hyaline, with walls distinctly thicker than those of basal marginal cells. Light microscope photographs of the significant characters are provided and its distinctions from closely related taxa are discussed.