Complete competitors cannot coexist, and the long-term stable coexistence of sympatric species is based on interspecific niche differentiation. The temporal niche differentiation of different species in the same distribution area is very important for their coexistence. In order to study the coexistence mechanism of sympatric species, we used camera trapping to conduct field survey on wild boar (Sus scrofa) and roe deer (Capreolus pygargus), which were both distributed in the same area in the Muling Japanese Yew National Nature Reserve from November 2018 to July 2021. We used the kernel density estimation method and the Jacobs Selection Index (JSI) to evaluate the daily activity rhythm and the selection for a period of the diel cycle, and also analyzed the relationship between the activities of the two species and the moonlight cycle by nonparametric tests. The results showed that the daily activity rhythm of roe deer was two higher peaks of activity in the whole year or in different seasons. Nevertheless, the activity pattern of wild boar showed obvious plasticity, which was unimodal in the whole year and the cold season, and bimodal in the warm season. The results showed that there was a moderate degree of overlap between them in daily activity rhythm (Dhat>0.59), and the degree of overlap was the highest (Dhat=0.65, 0.55-0.75) in warm season. In addition, in terms of time period selection, the roe deer were more likely active at dawn and dusk in the whole year and the cold season (0.170.32). However, the wild boar activities were more frequent during the day and dusk in the whole year and the cold season (JSI>0.3), and preferred to be active during the day in the worm season (JSI_day=0.86). Furthermore, two species of wild boar and roe deer were less active at night (JSI_night<0), especially for wild boar (JSI_night<-0.63). The frequency of roe deer behaviors differed significantly by moon phase (P<0.05), and roe deer were more active during the full moon period. However, the activity of wild boar was not related to the moonlight cycle (P>0.05). The study of temporal niche overlap of wild boar and roe deer provides research basis for the interaction between large carnivores and prey.