Anticoagulant properties of marine algae have been extensively studied for the last 60 years, among which green algae are considered as vital species with various bioactive substances. Heparin like compound was isolated from the seaweed "Chaetomorpha antennina". The activity w as studied following metachromatic dye method showing a yield of 2.3 mg/50 g. The anticoagulant activity of the extracted polysaccharide was assayed (in comparison with standard heparin) against the plasma protein thromoboplastin or thrombin of the sheep blood. In the agarose gel electrophoresis using acetate buffer, the band of the crude samples studied showed the band with similar mobility to standard heparin. The performance of the heparin extracted was fine and it resembles the commercial heparin to a greater extend and thus this species ("C. antennina") could be claimed as alternative potential source for the heparin with anticoagulant activity.