Abstract: From March 2017 to July 2021, the diversity of large and medium-sized mammals in the Xiaozhaizigou National Nature Reserve and its surrounding areas were continuously monitored by infrared camera technology according to the kilometer grid sampling scheme in Sichuan province. During the research period, with an intensive survey effort of 71593 efficient camera days at 230 locations (126 grids), a total of 28707 photographs and videos and 6071 independent and effective records of wild mammals were collected. A total of 22 wild mammal species belonging to 13 families and 4 orders were identified. Among them, 4 species were national I-class protected wild animals and 10 species were national II-class protected wild animals. Two species were evaluated as Endangered (EN), six species were Vulnerable (VU) and two species were Near threatened (NT) by IUCN Red List. The recorded Siberian Weasel (Mustela sibirica) was a new record in the nature reserve. The results showed that the distribution grid number of 18 species, including Chinese Goral (Naemorhedus griseus), Wild Boar (Sus scrofa), Himalayan Black Bear (Ursus thibetanus) and Golden Snub-nosed Monkey (Rhinopithecus roxellana), was not less than 10, and the corresponding grid occupancy rate and relative abundance index RAI were in the forefront. A large number of mammal species (18~20 species) were recorded in different functional areas of the nature reserve. There were many kinds of mammal species (7-13 species) clustered in different functional areas of the nature reserve and most of them had cross-altitude moving activities. The results of this study showed that the resources of rare and endangered wild mammals in the monitoring area were rich, the population number was large and the distribution was wide. To some extent, it indicated that the conservation work of the reserve had been effective for many years.