[Objectives] Niche differentiation is the foundation for the long-term steady coexistence of sympatric species. This study investigated the spatiotemporal distribution patterns and niche differentiation of Moschus berezovskii, Elaphodus cephalophus, and Muntiacus reevesi with similar body sizes and dietary habits in the same area, aiming to improve the understanding about the animal behavior and facilitate multi-species integrated conservation. [Methods] From October 2022 to September 2023, 160 infrared cameras were set up in Changqing National Nature Reserve, Shaanxi Province (Fig. 1). We employed kernel density estimation to analyze the monitoring data and thus reveal the temporal relationship of Mo. berezovskii, E. cephalophus, and Mu. reevesi. The daily activity rhythm curves were plotted. “CompareCKern” in “activity” package was used to compare their activity patterns. Then, the degree of the spatial overlap was calculated by the Pianka index, based on the relative abundance index of species at each site. Single-species occupancy models were adopted to analyze their spatial utilization characteristics, based on the detection history of the species at each site and 13 environmental factors potentially affecting their spatial distribution. All the analyses were conducted in R v.4.3.3. [Results] In 58 400 accumulated camera-days, we obtained 17 432 independent valid photos of wild animals, which included 426 photos of Mo. berezovskii, 1 274 photos of E. cephalophus, and 4 099 photos of Mu. reevesi. The overlap degree of the daily activity rhythms among species in different seasons was relatively high, with the overlap coefficients (?) between species consistently exceeding 0.82, while the spatial niche overlap was relatively low, with Pianka index (Oik) all less than 0.30 (Fig. 3). The curves of Mo. berezovskii, E. cephalophus, and Mu. reevesi showed an obvious bimodal pattern, with the first peak appearing in 5:30﹣7:30, 6:00﹣8:00, and 8:00﹣10:00, respectively, and the second peak all appearing in 17:30﹣19:30 (Fig. 4). For seasonal daily activity, Mo. berezovskii exhibited a typical bimodal pattern in spring and autumn, a unimodal pattern in summer, and three activity peaks in winter, while the activity curves of E. cephalophus and Mu. reevesi had two peaks with different timing and intensity patterns across the four seasons (Fig. 5). The common environmental factors influencing the spatial utilization of the three ungulates included elevation, distance to rivers, slope, relative abundance of predators, and vegetation type. Variations in preferences for vegetation types served as the principal driver of spatial segregation among the ungulates (Fig. 6). [Conclusion] These three sympatric species maintained stable coexistence through a high degree of spatial niche differentiation and temporal activity segregation, which effectively mitigated the competitive pressure despite high diel overlap.