Determination of chlorophyll a is one of the most common methods for measuring the primary production in the lakes and sea water. We studied Artemia Leach. dynamics and chlorophyll a fluctuation and their relationship in Urmia Lake. Sampling was performed monthly during one year (2007) at eleven sampling stations in Urmia Lake. Population dynamics analysis of Artemia from Urmia Lake suggested that the highest diversity in various Artemia morphological stages was present from May to July and the highest densities in March. On the other hand, no morphological stages were observed, at all stations in the lake, from January to April. The mean chlorophyll a concentration in Urmia Lake was 0.8 µg.L-1, and the highest and the lowest concentrations of chlorophyll a were measured in June and July with 2.53 µg.L-1 and 0.1 µg.L-1 respectively. According to the Carlson classification Urmia Lake was oligothrophic. Artemia biomass appeared in the mid spring and bloomed in the summer. Generally, there was a negative relationship between Artemia population and chlorophyll a.