The effect of elevated NaCl concentration (from 0.5 to 4.0 M) to the pigment content, O2 exchange and activities of some oxidative stress enzymes in the green alga Dunaliella salina was investigated. The optimum NaCl concentration (2.0 M) for the intensive biosynthesis of green pigments and function of the photosynthetic apparatus were established. The catalase activity increased up to 5.8 times and reached 0.5703 µmol min-1mg-1protein after 7 days of exposure to high salt concentration (3.0 and 4.0 M). The activity of catalase can be used as an indicator of alga cells’ resistance to salinity stress.