Abstract: In the autumn of 2m3 some beaver fossils were collected from Longdan，when the monograph on the Longdan Mammalian Fauna（Qiu et ., 2004）was under press · It is fint time to find beaver in Gansu Province．discovery not 0 y enlarged the list Of the I-ongdan Mammalian Fauna fmrn 31 to 32 taxa, further confirmed the ancientry of the Longdan Fauna, but also expanded the distribution area of the beavers to the Gansu Province also. In addition, the discovery threw some new light on the paleoenvironments of the Longdan area during the early Pleistocene.