Carotenoid is an important class of natural pigments widely existed in yellow,orange or red pigment of animals,higher plants,fungi and algae.Lots of carotenoids are contained in the peel and pulp residues as byproducts generated from the citrus processing.It is a rich resource in China,making it valuable raw materials for extracting carotenoids.Apart from the role of coloring,carotenoids contained in citrus is also involved in metabolism,immune response,hormone secretion and other physiological activities of the human body.The major types of carotenoids in citrus were reviewed and their biological activities as well as mechanism of action were summarized.