Abstract: Polyunsaturated acid GLA was extracted from Spirulina platensis, and the effects of different solvent, solid-liquid ratio, reaction temperature and reaction time on GLA yield and optimal process were also discussed.Besides, free radical scavenging activity, antioxidant capacity of GLA extract and protective effect on H2O2-induced HL-7702 cells were investigated, respectively.The results showed that the ethanol extraction at 70℃ with a sample-solvent ratio ( w /v) of 1 ∶ 12 for 90 min achieved the highest GLA yield of ( 8.3 ± 0.17) g·kg- 1 ( GLA/dry biomass) . The reaction temperature was the most significant factor among others. GLA extract exhibited strong inhibition effect on lipid peroxidation, of which the inhibitory effect of 10mg·L- 1GLA extract was even higher than that of 100mg·L- 1Vitamin C, while little activity was detected in the free radical scavenging activity, indicating that lipid environment might facilitate its antilipid peroxidation function.Moreover, the GLA extract exhibited protection effects on HL-7702 cells from oxidative damage induced by H2O2.