As the morbidity of metabolic syndrome like obesity and diabetes increases rapidly worldwide, the issue of nutrition (functional food) and health has drawn more attention. D-psicose, a rare natural ketohexose, has become a hot topic in functional food and health-care field because of its hypoglycemic and hypolipidemic function with good sweetness. This article mainly discusses the functional properties and biosynthesis research progress of D-psicose, together with the crystal structure of ketose-3-epimerase, to provide theoretical guidance for D-psicose-producing strain screening as well as improving the thermostability and catalytic efficiency of ketose-3-epimerase for industrial application.