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The unicellular alga, Haematococcus pluvialis is a potent producer of Ketocarotenoid astaxanthin. In this study, a comparison is made between the effect of salt and abscisic acid (ABA) on growth of greenish vegetative and red cyst cells in an Iranian strain (TMU) and German strain (SAG) of these algae. The results have shown that, the dry matter formation and the ratio of red cyst cells to green vegetative cells in TMU-strain are higher than those of SAG – strain. By Using of ABA, the changes from green vegetative cells to red cyst cells in two above mentioned strains are different and take place faster. In a 76-and 150 days – old TMU-strain algae, the number of cells increased 1.5 – and 4-time more respectively by use of abscisic acid, which is related with induction of encystment of vegetative cells. Therefore it could be demonstrated that ABA as a regulatory processes, which involved in aging Process, is essential for encystment and dry matter formation due to increasing the number of life cycles of Haematococcus cells in a constant period.