||Health foods (Nutraceiuticals) play the critical role on the global food market in 21st century, while the health seafood area is the new era of functional foods and exposed the great potential. Synechococcus sp., a member of cyanobacteria family, containing phycocyanin is one of the major light harvesting pigment-protein which exhibiting diverse antioxidation capacities, anti-inflammatory, neuroprotective and hepatoprotective effect. The main objectives of the study are using concentrated Synechococcus sp to investigate the optimal extraction conditions by various methodologies and evaluate the antitumor activity by employing purified phycocyanin. The results indicated that Freezing -thawing in combination with distilled water was the best method for extracting phycocyanin from Synechococcus sp.U2. The crude extracts was concentrated up to 20 fold by ultrafiltration and consecutively purified by butyl- sepharose and DEAE- sepharose resin. When analyzed by SDS-PAGE, Synechococcus sp. U2 phycocyanin migrated as two bands having an apparent molecular weight of 18.4 and 17.1 kDa. The purity extracts of 90μg/ml from Synechococcus sp.U2 scavenged DPPH 、superoxide and H202by 92.1% 、82.5% and 61.8%, respectively. The dosage of purified phycocyanin, 0.1, 0.5, and 1.0 mg/plate were used, showed no toxicity and mutagenicity. The purified phycocyanin extracts from Synechococcus sp.U2 indicated the best antimutagenic effect when the concentration of 1 mg/plate phycocyanin was employed. The purified phycocyanin extracts was stable over pH=7 at 4℃without light. In the presence of metal ions, the content of phycocyanin was reduced by adding 100 mM HgCl2 and CuSO4 and only less than 30% residual left. In related to chemical additives study, the content of phycocyanin was reduced 85.2% and 78.1% respectively by adding 100 mM HgCl2 and CuSO4. The antitumor study revealed that the phycocyanin has the effect on the viability of HepG2 and Hep3B cells, and the IC 50 for those two cells are 30 μg/ml and 70 μg/ml, respectively. However, no significant effect was observed on the viability of normal 3T3 cells. The microscopy observation indicated that the higher concentrated phycocyanin was employed, the more intensive shrinkage of HepG2 cells was found.