The Lake Urmia is the greatest hyper saline Lake in the world. This lake, located in Azerbaijan area, Northwest of Iran is an intra-continental sedimentary basin. Its area is about 6000 km² with an average water depth of 6 meters. Hydrochemistry of the water resources of the basin showed mainly chloridic and sulfidic composition due to the geology of the surrounding areas and its variable lithology and Inlet water are supplied from the permanent and seasonal rivers. The hydrochemical investigations were carried out over a time period from 2007 to 2012 using previously published data together with newly collected water samples. 120 samples were collected during 6 years. The analaysis results showed Na-Mg-Cl type of the brinefrom  2007 to 2010, which is comparable with the Great Salt Lake in the USA. The chemical composition of lake in 2007 showed the percentage of sodium is higher than Magnesium. In 2011 and 2012 water composition is HCO3<<Ca+Mg. That is, the path of brine composition on the Eugster and Hardie flow diagram has changed from row III2b (Na-Mg-Cl) to (Mg-Na-Cl) in 2011 and 2012 after halite crystallization and may finally result in Mg-Cl-SO4 brine type in the future. The Sodium to Magnesium ratio is 5.12 in 2007. However, this amount in 2011 is 0.68 and 0.56 in 2012. In future, with Increasing ofevaporation, the Magnesium to sodium ratio increases and  chemical compositions of the brine in the north and south of the Shahid Kalantari Highway experience more difference.