China’s mammalian fauna is unique: it possesses the endemic species and genera of the Qinghai-Tibetan Plateau; it has the relic families, Ailuropodidae and Lipotidae, of the Tertiary Period; more than half of the species of the Ochotonidae in the country are endemic; furthermore China is also the country with world most abundant ungulate diversity. In the new millennia, changes to the taxonomy of mammals of world were proposed. New mammalian species and new mammals were reported in China. Thus it is necessary to renew the inventory of China’s mammal diversity. During the compiling of The Red List of Endangered Species in China: Mammals, we collected the available data on China’s mammals (including those of Taiwan) and formed The Checklist of China’s Mammal Species 2015. For taxonomy of orders, we followed the existing theory using molecular phylogeny whereas for the classification of families and the taxa below family level, we followed the A Complete Checklist of Mammal Species and Subspecies in China: A Taxonomic and Geographic Reference by Wang (2003) and Mammal Species of the World: A Taxonomic and Geographic Reference by Wilson & Reeder (2005). We also adopted Ungulate Taxonomy by Groves & Grubb (2011) to classify the ungulates in China. The initial list included species recorded in taxonomic books and field guides, new species and new records in literature before March 31, 2015. After five evaluation meetings and two rounds of evaluation by correspondence, we finalized The Checklist of China’s Mammal Species 2015, which includes 12 orders, 55 families, 245 genera and 673 species. Among those species, 18 new species (including 11 discovered with molecular biology methods, the validity of the species are still in dispute among zoologists), 18 new species records in country, and 60 subspecies were elevated to the status of species were added to the checklist. According to literature and expertise, we deleted 52 species which are not found in China. Of them, specimens of some species were collected only once, and then never been found again during following surveys. Taxonomists hold different opinions on 20 Glires, and those species need further investigation. Compared with the data of IUCN Red List (2014), the number of mammal species in China recorded in the study is surpassed that of Indonisia (670), China became the country with the most abundant mammal species in the world. The mammals in China accounted for 12.3% of the world total numbers of mammalian species. There are 150 endemic mammals in China, which accounted for 22.3% of the national total. 43% of the species in Lagomorpha are endemics to the country. The endemic ratio of Ochotonidae is even higher, 52% of the total. Endemic ratio of Eulipotyphla is 35%. About one fifth of Primates, Chiroptera and Rodentia in China are also endemics, including 12 new bat species discovered in the country during recent decade. The Checklist of China’s Mammal Species 2015 provides the most updated baseline information for biodiversity research and conservation.