Abstract:The fertile plants of Grimmia ulaandamana J. Muñoz, C. Feng, X.L. Bai & J. Kou were recently discovered in Inner Mongolia, China. The characteristics of mature sporophytes, as well as female and male plants were described. The capsule of sporophytes is longer than the arcuate seta, capsular surface with longitudinal wrinkle, epidermal cell wall of central capsule was thick, ring cells square or short rectangular, the opercle with beak. The peristome teeth had papillose and bifurcated at upper part, separated at base, the base of peristome teeth is lower than mouth of capsule. There is a layer of small cells between epidermal cells and peristome teeth, the trabeculae of capsular bones are strongly protruding about 1/3 of the base. Capsular cap base intact. The innermost female bracts are larger the leaves at stem. Grimmia ulaandamana had important morphological variation, the fertile plants could provide more evidence to distinguish from the most similar species G. elatior. The novel description and illustrations of sporophytes were presented, and the phylogenetic significance of sporophytes was discussed.