Codium cylindricum, a common green algae of the genus Codium, is abundant in the surrounding waters of Penghu, especially in April to July. Previous literatures indicate that Codium cylindricum could inhibit obesity, inflammation and angiogenesis;
however, the information about bioavailability and biotransformation is deficient. Therefore, we analyzed and utilized the active ingredient of it. The result showed that it comprises 92.76±0.12 of water. The result of heavy metal test was as follow: 2.04 ppm of total arsenic, 0.06 ppm of lead, cadmium and mercury undetected. The content of amino acid was as follow in order: Glutamic acid (154.72 mg/100g), Aspartic acid, Leucine, Alanine, and Lysine. The content of fatty acid was as follow in order: 29.03% of Palmitic acid and 21.41% of α-Linolenic acid (ALA). In addition, it also contains Polyunsaturated fatty acid, such as γ-Linolenic Acid, α-Linolenic acid, and eicosatetraenoic acid, which could regulate human physiological functions. The results of water extraction and enzyme hydrolysis with Viscozyme, Everlase, Flavourzyme, Pepsin, and Celluclast are as follow. The highest values of total sugars content were obtained from enzyme hydrolysis with Viscozyme. The higher values of sulfate content were obtained from water extraction whether molecular weight is over or below 3000 kDa; moreover, the highest value is 269.58±0.52μg/ml under a concentration of 1200mg/ml. The top two values of carotenoid content were obtained from water extraction (2.31±0.40mg/ml) and enzyme hydrolysis with Viscozyme (1.88±0.25 mg/ml). The bioactive material of Codium cylindricum could be used as natural food antioxidant and antimicrobials, and furthermore, be used in pharmaceutical and cosmetic industries. It worth further study and development.