Samples from two sites of the surface of Dokan Lake were collected monthly over period of 8 months for physico-chemical analysis of water and investigated algal compositions. In this context, several limnological parameters were evaluated during the period from September 2008 to April 2009. The included physical and chemical parameters were: Air and water temperature, electrical conductivity, total dissolved solids, pH, alkalinity, total hardness, dissolved oxygen, Ca²⁺, Mg²⁺, Na⁺, K⁺, SO₄ ^--, Cl^- , and the concentrations of nitrite and phosphate. The study revealed that the air and water temperature ranged from 10 to 33 °C and 9 to 30 °C, respectively. Conductivity was in the range of 240-430 µS/cm, TDS was 161 to 280 mg/L, pH range was 7.3 to 8.0. Dissolved oxygen ranged between 5.5 to 9.2 mg/L. Calcium and magnesium concentrations varied from 30 to 52mg/L and 14 to 24 mg/L, respectively. Potassium and sodium ranged between 3.8-6.0 mg/L and 1.1-2.2 mg/L, respectively. Sulfate value varied from 130-224 mg/L and ranged between 18-25 mg/L for chloride. High value of nitrate was recorded. A total of 30 species of algae were recorded of which 14 species belong to Bacillariophyceae, 8 species belong to Chlorophyceae, 5 species to Cyanophyceae, 2 species to Pyrophyta, and one species to Euglenophyceae.