A new species of philometrid nematode (Nematoda: Philometridae), Philometroides buirnurensis sp. n., is described and illustrated on the basis of female specimens from subcutaneous tissues of the inner surface of the abdominal cavity and the bile duct of cyprinid fishes Leucisuus waleckii (Dybowski), 1869 (type host), Pseudaspius leptocephalus (Pallas), 1776 and Hemiibarbus labeo (Pallas), 1776, from the Buir Nur Lake, a boundary lake between China and Mongolia, on southwest of the Hulun Buir League in the Inner Mongolia Autonomous Region of China. The new species distinctly differs from its congeners mainly in that the posterior half of its body is tapered and conspicuously narrower than the anterior region and that both the head and tail ends are rounded. The cuticular bosses are distributed extensively at both ends but poorly on the middle part of the body. The most peculiar feature of the bosses situated at both ends was their lobe- or rodlike shape and their transverse orientation. Four pairs of submedian outer cephalic papillae and 1 pair of caudal papilla are all relatively large. The new species differs from the most similar congener, Philometroides ganzhouensis Yu, 1998, in having 4 inner cephalic papillae and in the presence of 2 caudal papillae in mature specimens.