Abstract: Social monitoring refers to animals cognition of the social environment for adaptation and improving their fitness. In order to understand the frequency and influencing factors of individual social monitoring behavior of all-male unit in black-and-white snub-nosed monkey (Rhinopithecus bieti) under a multi-level social organization, from July 2017 to August 2018, the data of scanning behavior and aggression-submissive behavior of 8 individuals in the all-male unit of R. bieti in Xiangguqing of Baima Snow Mountain National Nature Reserve were collected by using 5-minute focus animal and all-occurrence recording method, and the frequency differences of monitoring behavior in different seasons and grade groups were compared. The results showed that the frequency of scanning behavior was 0.67 ± 0.19 Times /min (n = 8, 0.37-1.01). There was a difference in the frequency of scanning behavior between winter and summer (Z = 7.36, P < 0.001), and the frequency of scanning behavior in summer (0.80 ± 0.24, n = 8) was higher than that in winter (0.50 ± 0.21, n = 8), which may due to high competitive pressure of reproductive and mating in summer. The frequency of scanning behavior in different grade groups was different (H = 62.37, df = 2, P < 0.001). The low grade group (0.85 ± 0.14, n = 3) was higher than the middle grade group (0.68 ± 0.28, n = 2), and the middle grade group was higher than the high grade group (0.49 ± 0.12, n = 3), which indicated that low-grade individual spent more time on social monitoring within all-male unit of R. bieti. Therefore, our finding found that the frequency of social monitoring of R. bieti in all-male unit is affected by the reproductive season and grade group. Adult males can reduce the attack by the resident males of reproductive units through social monitoring, and the social monitoring of young and juvenile males can reduce the direct conflicts within the all-male unit.