Carotenoids are one group of the most widespread and important pigments, and one of the major sources of natural carotenoids is seaweed. By chemical extraction, chromatography and spectroscopy, identification and quantification of carotenoids were carried out in various seaweeds, including Chlorophyta, Rhodophyta and Phaeophyta. It was demonstrated that carotenoid content in green algae is the highest, usually two or three times more than the other two. The structural analogs of carotenoids in green algae are also more variable than those in red and brown algae. The major carotenoids are zeaxanthin and lutein in green algae. zeaxanthin and violaxanthin in red algae, fucoxanthin and violaxanthin in brown algae. Among the seaweeds investigated, Codiumn fragile is the most potential resources for carotenoids with high content and structural variations. The chemical composition and contents of carotenoids could be used as possible markers of chemotaxonomy in marine algae.