Phytoplankton species composition as well as amount of Chlorophyll-a and their relation to physico-chemical parameters were studied. The samples were collected monthly from October 1996 until September 1997 in two stations, i.e. Lavan and Douberkeh coastal waters. In this study, 65 phytoplankton species related to 3 groups of diatoms, dinoflagellats and Blue-Green Algae (24 genus and 44 species of diatoms, 6 genus and 18 species of dinoflagellats and 3 genus blue-green algae) were identified. Diatoms and dinoflagellats were abundant during periods of low salinity and temperature (November-May), while blue-green algae were abundant from July till September. Although the amount of chlorophyll-a was higher during the periods of low salinity and temperature, there was not statically significant difference between the two stations and different seasons (p < /em>>5%). Also, there were not significant differences between such physico-chemical factors as temperature, salinity, pH and oxygen content. Transparency between the two stations showed significant differences (p < /em><5%). Correlation matrix test showed no relationship between physico-chemical parameters and the amount of chlorophyll-a in two stations. The results suggest that increasing the temperature and/or salinity cannot cause significant reduction in chlorophyll-a amount in Lavan and Douberkeh regions.