Orinus is an alpine genus with important economic values in the grass family (Poaceae). There are six species in it and all of them have stronger adverseresistant characteristics, and they are the important resources for improving and applying agricultural breeding and animal husbandry. Meanwhile, the discriminative characters are obscure among these species. Two taxa of Orinus (Poaceae) from the QinghaiTibet Plateau are taxonomically revised on the basis of herbarium materials, field observation, generalized morphological analysis and laboratory examination. O. longiglumis and O. tibeticus, O. alticulmus and O. anomala are reduced to synonyms of O. thoroldii and O. kokonorica.