Seaweed pigments can be roughly divided into three classes: chlorophyll, carotenoid and phycobiliprotein. The carotenoids are among the most widespread and important ones. Because of their ubiquitous occurrence, different functions and interesting properties, carotenoids are the subject of interdisciplinary research in chemistry, biochemistry, biology, medicine, physics, and many other branches of science. Based on the research results worldwide, this article systematically introduces the structure, classification, properties and functions of each seaweed carotenoid, and makes prospects for their application to the food industry, medical treatment, and so on.