Abstract: The occupancy model can be used for infrared camera research on large and medium-sized mammals. The model is aimed to understand the proportion and spatial distribution of the area occupied by a species or its suitable habitat, and to assess the impact of environmental factors on the species occupancy. In this study, 40 infrared cameras were deployed for monitoring in Fanjingshan and Chishui Alsophila National Nature Reserves from April to July 2019, respectively. Subsequently, 22 mammal species within 4 orders and 12 families, and 19 mammal species within 4 orders and 10 families were captured in the two nature reserves, respectively. The survey show that the relative abundance index of large and medium-sized mammals in both the two reserves was higher in the Tibetan macaque (Macaca thibetana), wild boar (Sus scrofa), Reeves' muntjac (Muntiacus reevesi) and tufted deer (Elaphodus cephalophus). Furthermore, the occupancy status and influencing factors of the above four species were analyzed by using the occupancy model. The results show that the occupancy rates of the four species were 0.67, 0.53, 0.37, 0.58, and the detection probabilities were 0.20, 0.21, 0.31, 0.27, respectively. The occupancy of Tibetan macaque was negatively affected by elevation and slope, and positively affected by shrub coverage. The wild boar was negatively affected by shrub coverage and slope, but positively affected by elevation. The Reeves' muntjac was negatively correlated with shrub coverage, and slightly with nelevation, but positively affected by slope in some extent. The tufted deer was positively affected by shrub coverage, and negatively affected by slope. Finally, the author further summarized the application scope of the occupancy model and the existing problems in the researches, and it is expected that this method coiuld be widerly applied in thefuture researches.