Marine habitat represents about 70% of our planet. Microbial populations including bacteria, fungi and algae represent a base of food pyramids in this environment. The exudates of microbial cells (like polysaccharide) in the marine environment play an important role in energy cycling between the surface and the bottom in the sea by aggregation of small molecules causing them to sink. So it plays an important role in carbon sequestration and re emission through what called biologic pump. On the other hand, microbial polysaccharides help the microbial cell itself to colonize hydrophobic surfaces forming biofilms and tolerate drastic conditions like heat, salinity and cold stresses. Marine microbial polysaccharides are characterized by unique properties making them a good source of bioactive agents that can be used in many fields as anti-tumor, antiviral, antioxidant, anticoagulant, food and feed applications. An overview of the role of polysaccharide in the marine environment, its advantages and applications will be presented.