China is a country with rich marine mammal resources, with a total of 46 species including 38 species of Cetacea, 1 of Dugongidae, 5 of Pinnipedia and 2 of Lutrinae,which provides Chinese scientists with excellent opportunities to study marine mammals. Since 1920s, Chinese scientists have carried out a series of studies on the biology and conservation of marine mammals in Chinese waters through multidisciplinary methods. Especially some important advances were made on the biology and conservation of the baiji (Lipotes vexillifer), finless porpoises (Neophocaena spp.) and Chinese white dolphins (Sousa chinensis), evolutionary history and adaptive mechanism of secondary aquatic adaptation, and population genetic diversity etc, which not only improved our understanding of understandings of marine mammals in China, but promoted their conservation and management. Here we reveiwed the research progresses of marine mammals in China from seven aspects such as diversity, ecology and conservation biology, morphology and anatomy,
breeding and reproductive biology, acoustic behavior, genetic and evolutionary biology, and genomics etc. In the future, some more attention should be paid to the evolutionary history and adaptive mechanism of secondary aquatic adaptation, whereas it is of great importance to reveal the mechanisms underlying the endangerment of marine mammals and provide adaptive strategies for their conservation and management.