Abstract: After eight years field survey,The Yunnan snub-nosed monkey (Rhinopithecus bieti),an endangered species endemic to China,was estimated to be 1000-1500 individuals spread in 13 natural groups.All these groups were isolated due to fragmentation of its habitat,therefore,the genetic diversity in each of the groups or populations was low.This species was confined to the area between Jinshajiang (upper part of the Yangtze River) to the east and Lancangjiang (upper part of the Mekong River) to the west.The northernmost group was located in Xiaochangdu (29°20 N,98°37 E),and the southernmost group in Longmashan (26°14 N,99°15 E).The species was the non-human primate species found at the highest elevations,and this was the prime forces in the evolution of the monkey s uncommon morphological and behavioral adaptation.The dominant conspicuous tree canopy of its habitat was fir dotted with a few small larch patches,and most of the understorey was either rhododendron (when above 3700 m asl.) or bamboo (when lower than 3700 m asl.) scrub.The monkey spent 87% of its feeding time in fir tree,and its main food was the lichen (Bryoria nepalensis),an epiphyte on fir.About twenty-two percent of its time were spent on the ground or rock outcrops during the day time.Its home range might be over 100 km2.Monkey groups sometimes went up to a few hundred meters above tree line (4700 m asl.) and cross wide alpine meadow patches on top of snow mountain.Further conservation action on this precious animal should be implemented as soon as possible,and this might be extremly important to protect the ecosystem in the watersheds of both the Yangtze River and the Mekong River.