Carrageenans are gel-forming hydrocolloids extracted from the cell walls of marine red algae, such as Eucheuma, Chondrus, Gigartina, Hypnea.

There are many kinds of algae in vast sea area and the inland water in China, such as brown alga, green alga, red alga, blue- green alga and microalgae and so on.

The relationship between the chemical composition of fucoidan separated from Sargassum fusiform and its anticoagulant activity was studied.