[Objectives] The coexistence of competing species in the same area is often achieved through ecological niche differentiation. The Grey Snub-nosed Monkeys (Rhinopithecus brelichi) and Tibetan Macaques (Macaca thibetana) occupy the same area in the Fanjing Mountain. This study compares the ecological dispensing characteristics of the two sympatric primary species, and it is helpful for better protection of the endangered species. [Methods] From December 2020 to June 2021, we conducted camera trapping survey in Fanjingshan National Nature Reserve, Guizhou, in order to explore the ecological position of Grey Snub-nosed Monkeys and Tibetan Macaques, with 24 infrared cameras placed in Xvjiagou, Huguo Temple, Fanjingshan Village, and Lengjiaba in Fanjing Mountain Reserve (Fig. 1). Analysis of differences in the daily activity rhythms of two primate species was performed based on images captured by infrared cameras. Based on the independent events filmed by the infrared camera, the relative activity index (RAI) of each time during each period time is calculated every 2 hours. The ecological niche differentiation of the two species was analyzed using the altitude, feeding behavior, and emergence time, and the ecological niche differentiation patterns of these two species of primates with the same domain distribution were obtained. [Results] The results showed that: (1) Eighteen cameras captured Tibetan Macaques and four cameras captured Grey Snub-nosed Monkeys, while three cameras captured both Grey Snub-nosed Monkeys and Tibetan Macaques. Photos and videos taken continuously by the same camera within 30 minutes were grouped into the same trigger event. A total of 23 photos of Grey Snub-nosed Monkeys over eight events were obtained, while 373 photos of Tibetan Macaques over 95 events were obtained. There were no photos of Grey Snub-nosed Monkeys and Tibetan Macaques appearing together (Table 1). (2) The distribution areas of Grey Snub-nosed Monkeys and Tibetan Macaques in Fanjing Mountain in winter and spring partially overlapped at altitudes of 969 to 1 277 meters, with a certain degree of competition (Table 1). (3) The activities of Grey Snub-nosed Monkeys were influenced by those of the Tibetan Macaques, and Grey Snub-nosed Monkeys were in a competitive position between the two; the peak activity of Tibetan Macaques occurred about 2 hours later, and the two primates showed a clear divergence in peak activity time (Fig. 2 & Fig. 3). (4) The two species exhibited different feeding behaviors (56.5% of Grey Snub-nosed Monkeys preferred to feed in trees, while 61.9% of Tibetan Macaques preferred to feed on the ground), and there was a clear differentiation between the two in terms of feeding behavior (Table 2). [Conclusion] The differences in activity time and activity space formed different dimensions of differentiation in ecological niches, and feeding on different foods helped them to avoid direct competition for food resources. It can be assumed that the co-distributed Grey Snub-nosed Monkeys and Tibetan Macaques in Fanjingshan Mountain have achieved ecological differentiation and coexistence through these means.