The Red-shanked Douc langur (Pygathrix nemaeus) is the apes species, belonging to the leaf monkey (Colobinae) family which is under threat of extinction. Up to now, Bach Ma National Park is the only region in Thua Thien - Hue province recorded the existence of this species. However, there are great insufficience of profound and updated research on the species population and distribution. Using forest inventories in addition to the interviews of hunters and forest rangers in the National Park, 4 groups of P. nemaeus and one single individual were recorded, with the total number of 35-43 members and 7- 9 individuals per groups distributed in the subdivisions of 384, 230, 229 and 210. In Bach Ma National Park, The Red-shanked Douc langur lives in the range of 1000 to less than 1400 meters in the natural dosed forest and restored forest. These area are medium, rich and pristine forests with overlapped canopies and the concentration food trees. However, their foraging range comes down to 900 meters. It is really necessary to expand the survey area to similar ecological subdivisions in order to supplement the information about the species population and their actual distribution to serve as the baseline foundation for zoning and protection of the species. Bach Ma National Park should use their forest rangers to hold regular patrols for monitoring and protecting these subdivisions in order to ensure the existing and development of this species.