The Sichuan snub-nosed monkey (Rhinopithecus roxellana), a rare primate in China, has suffered rapid population decline over recent decades. This primate inhabits the temperate forests in the mountainous highlands of Sichuan, Shaanxi, Gansu, and Hubei Provinces in China, at 1500 m to 3400 m above sea level. Most of the previous studies on Rhinopithecus roxellana have been carried out in Shaanxi Province, and there have been fewer studies in Sichuan Province. A population survey conducted in Sichuan Province in 1994 showed that the species is widely distributed in the forests along the mountainsides of Minshan, Qionglai, and Liangshan, with the majority residing in the Minshan Mountain forests. Jiuzhaigou National Nature Reserve is located on the southern slope of the Minshan Mountains in northwest Sichuan Province. R. roxellana is a multi-level social primate with groups consisting of several units, each comprising a breeding male, several adult females, and their offspring. We sought the help of the local villagers to obtain information on the approximate distribution of the monkey population in the nature reserve. We used this information to select the study regions where the distribution, social structure, and population of R. roxellana were measured in an attempt to analyze their adaptability in the Jiuzhaigou National Nature Reserve, Sichuan Province. The data were collected from February to May 2014, and during the last 75 days of this period, we used a V-shaped transect for the survey. When a group was observed, we recorded the height at which the group members were observed, the location and time of encounter, direction of the group's movement, sex and age of all individuals, habitat structure at that location, and the plants species on which the group was feeding. Our survey results confirmed that 4 groups, 19 One Male Units (OMUs) and 3 All Male Units (AMUs), resided within the reserve. One of the 4 groups that we followed for 8 days ranged across areas from Jiuzhaigou to Baihe. We confirmed 296 individuals in the 4 groups, with the OMUs having an average of 12.7 members, of which 38% were adults, 53% were juveniles, and the remaining 9% were infants. The average ratio of adults to juveniles was 1:1.39, while the ratio of females to males was 3.84:1. The primary distribution of the social groups was in Zarugou in Jiuzhaigou Nature Reserve, an area on the southern face of the mountain that receives adequate sunlight and is near the Baihe Nature Reserve. The groups were observed to be the most active in coniferous forest, at heights between 2400 m and 3550 m. When compared to the Qinling golden monkeys, Jiuzhaigou monkeys showed the following differences in body size and color of the hair on their backs:adult Jiuzhaigou males seemed stronger than the Qinling monkeys and had longer hair; the hair on the backs of adult Jiuzhaigou females was less golden and more black, and most of them had caruncles at the corners of their mouths; and the hair of juvenile Jiuzhaigou monkeys was whiter than that of Qinling monkeys. Thus, these two groups may be different subspecies, based on their morphological differences.