Abstract: The stresses of high salinity (110) and low salinity (0) on the (·OH^-) content, hydrogen peroxide (H₂O₂) content, malondialdehyde (MDA) content, superoxide anion (O₂^-·) content, superoxide dismutase (SOD) activity, catalase (CAT) activity, ascorbate peroxidase (GSH) activity and chlorophyll fluorescence parameters including the maximum photochemical efficiency (Fv/Fm), apparent photosynthetic electron transport efficiency (ETR), non-photochemical fluorescence quenching (NPQ) and the actual photosynthetic efficiency［Y(II)］ of Porphyra (Pyropia haitanensis Z-61) blades were studied in order to explore the tolerance mechanism of the blades at different time (0h, 4h, 8h, 24h and 4h after restoration). The results showed that under high and low saline stresses, the content of H₂O₂ and ·OH^-increased gradually with time, while the content of O₂^-· changed insignificantly after 4h stress. Compared with the high saline stress, the contents of H₂O₂, O₂^-· and ·OH^-in the blades of lower saline stress were higher and the content of MDA in the membrane lipid peroxides increased significantly. It indicated that the oxidative damage of the blades was much serious than that in the high saline stress. Under 24h high saline stress, the activity of SOD reached the maximum, and the activities of CAT, APX and GSH showed an increase in the first and then decreased.Under low saline stress, the activities of SOD and GSH were increasing, respectively, and the activities of CAT and APX increased first and then decreased. In addition, the chlorophyll fluorescence parameters decreased with time under both low and high saline stress. The results showed that the photosynthesis of the blades was inhibited, and the algae ensure the normal survival by maintaining a higher antioxidant enzyme activity to improve the ability of active oxygen scavenging.