Primates are a main disperser of plant seeds in forest ecosystem, which contribute to the regeneration of forest vegetation. However, due to the limitation of research methods, the potential of primates seed dissemination are often underestimated. In order to fully understand the seed dispersal ability of primates in temperature forest, we evaluated the seed dispersal ability of a rare and endangered primate species black-and-white snub-nosed monkeys (Rhinopithecus bieti) using two methods. We used direct observation method (instantaneous scanning sampling method) to collect the activity time budget data of R. bieti in Mt. Lasha within Yunling Provincial Nature Reserve, Yunnan, China from Nov., 2018 to Oct., 2019, and counted percentage of time spent on fruits by month. At the same time, we collected the feces of R. bieti and sorted out plant seeds in feces, and counted percentage of feces with seed residues each month. Then we evaluated seed dispersal ability of R. bieti of the above two methods and their differences. Our results found that the number of months of fruit feeding by R. bieti was 6 months (Jul.-Dec.) according to direct observation method, with an average time spent on fruits was (15.31±20.15)%, and a total 13 species of fruits were eaten. However, fecal analysis method showed that seed residue in feces of R. bieti were detected throughout the year, and the average percentage of feces with seed residue was (35.19±35.43)%, of which the percentage of seed residues in feces was more than 50%, and a total of 18 species of fruits were eaten, from September to January of the following year. Based on the two methods, the R. bieti fed total 20 plant species of fruits in Mt. Lasha, indicated that R. bieti had a high ability of seed dispersal. The direct observation method could determine the number of species of fruits consumed by R. bieti, while the fecal analysis method could reflect the number of species and number of seeds that dispersed by R. bieti. We also found that R. bieti ate fruits all year round, which increased the understanding of the fruit sex ratio and the month of seed dispersal of R. bieti. Therefore, our study suggested that we can comprehensively evaluate the seed dispersal ability of R. bieti and other primate species by combination of two methods, which will be benefit to evaluate their effectiveness in plant seed dispersal and their contribution to forest ecosystem regeneration, and provided a new perspective of understanding that primates could promote the ability of forest ecosystem regeneration through seed dispersal.