In order to understand how the sympatric distribution of ungulates maintains interspecific relationships to achieve stable coexistence in a complex mountain forest habitat, this study analyzed the spatial and temporal ecological niche characteristics of sympatric distribution of the Chinese serow (Capricornis milneedwardsii) and the Chinese goral (Naemorhedus griseus) in the Minshan, Qionglai, Daxiangling, Xiaoxiangling and Liangshan mountain systems in Sichuan Province based on species distribution models and daily activity patterns. The results showed that:(1) in the five mountains of Sichuan Province, the suitable habitat area of the Chinese serow was 28006.07 km², accounting for 26.18% of the total area of the study area, among which the highly suitable habitat area was 10015.90 km². The suitable habitat area of the Chinese goral was 21073.32 km², accounting for 19.71% of the total area of the study area, among which the highly suitable habitat area was 8396.22 km². (2) Niche overlap indices, calculated by ENMTools, showed that the two species had high overlap (D=0.776, I=0.949). The Chinese serow and the Chinese goral had high selection similarity on environmental variables and large habitat overlap area. In terms of spatial distribution, the main overlapping areas of the Chinese serow and the Chinese goral suitable habitats are the Minshan Mountain and the Qionglai Mountain. And, the overlapping area of suitable habitats is 12967.50 km², accounting for 46.30% and 61.54% of their total suitable habitat area, the overlapping area of highly suitable habitats was 5955.28 km², accounting for 59.46% and 70.93% of their highly suitable habitats. (3) There was no significant difference in daily activity rhythm between the Chinese serow and the Chinese goral (P=0.534), and the overlap index was 0.812. (4) They were exploitation competition species, and the presence of the Chinese goral significantly affected the daily activity rhythm of the Chinese serow (P=0.016). They increased their diurnal activity intensity and enhanced the intensity and duration of their peak activity when they were sympatric distribution. In this study, the spatial and temporal niche characteristics of the Chinese serow and the Chinese goral were analyzed, and the coupling relationship of population coexistence and interspecific competition in spatial and temporal niche was revealed. This study, on the one hand, is helpful to deeply understand the spatial and temporal niche characteristics of sympatric distribution animals, the coexistence mechanism and interspecific competition of the related species. On the other hand, it provides a scientific reference for the conservation of rare wildlife populations and habitats, such as ungulates.