Abstract: In this study the effects of (20, 30, 40, 50 ppt) salinities and (2500, 4500, 6500 Lux) luminances on the changes of chlorophylls, carbohydrates, proline and proteins of unicellular microalga Tetraselmis chuii have been studied in the controlled conditions. The results indicated that the amounts of all of these parameters have been influenced by the salinity and light intensities. The amount of proteins have not been changed significantly in all cases. Carbohydrats and proline contents as osmoregulators have been increased in stress conditions. But the amount of chlorophylls have been reduced while carotenoids contents have been increased. So we conclude that as like as higher plants high and low (in halophytes) salinities and light intensities cause some biochemical changes in unicellular green microalgea. In many cases adaptation mechanisms to stress conditions are the same in them, such as increased accumulation of proline and carbohydrates and some changes in pigments and protein contents of the cells of organism. Due to these results and other similarities, perhaps higher plants have been originated from these green unicellular algae.