To have more overall investigation, field surveys were carried out to investigate the diversity and distribution of mammals in Yanqing district by line transect method, camera-trapping, live traps, cave survey, and interview survey, Beijing from 2017 to 2018. We analyzed the factors influencing the mammal abundance and distribution. Twenty one species were recorded (belonging to 7 orders and 15 families). By the relative abundance index (RAI), Wild Boar (Sus scrofa) was the highest detected species (28.27%), followed by Hog-badger (Arctonyx collaris, 21.47%) and Asian Badger (Meles leucurus, 13.79%), the Asian Lesser White-toothed Shrew (Crocidura shantungensis, 0.17%) and north China Zokor (Myospalax psilurus, 0.17%) were the least two species in number (Table 4). By the distribution, Wild Boar is the most widely distributed mammal, accounting for 84.21% of all survey grids, followed by Hog-badger and Asian Badger, 73.68% of the total number of survey grids. Asian Lesser White-toothed Shrew and other 5 species only have one record in the grid, 5.26% of the total number of grids (Table 1). The highest species richness was found in Songshan National Nature Reserve and the Wild Duck Lake Wetland both located in southwestern part of Yanqing. The minimum species richness occurred in Shuitou Valley Scenic Spots and Jiuyanlou Scenic Spots in the northeastern section of Yanqing (Fig.1). The main negative influence factors on the mammal diversity is recognized as “water resource availability” and “distribution of human activity”. On the purpose of better protection for the diversity of mammals in this region, we recommended that: (1) building diversion works or establish the permanent water points in water-deficient regions, and (2) strengthening the wildlife conservation education in non-protected areas to reduce the interference of tourism such as mountaineering to wild mammals.