Fat is an important nutrient component of dairy products, and the category, content, and fat composition is closely related to nutrient requirement in human. However, the kinds and contents of fatty acids in milk are changed after fermentation.The article introduces differences in fat composition between dairy products and others, as well as the impacts of fermentation on dairy fats. The research progress of fat detection techniques, including high efficiency liquid chromatography, gas chromatography-mass spectrometry (GC-MS), and infrared spectroscopy (IRS) is reviewed.