The present study was carried out to determine the monthly variations of physico-chemical parameters in water samples from Chiffa river at Blida, North West of Algeria from April to August 2006. Water samples were analyzed for physico-chemical parameters and the results showed their monthly variations as follows: pH 7.5-7.6, electrical conductivity 0.87–1.06 mS·cm−1, nitrate 0–7.00 mg·L−1, nitrite 0–0.28 mg·L−1, ammonia 0–0.03 mg·L−1, phosphate 0–0.94 mg·L−1, sodium 19.3–47.0 mg·L−1, chloride 35.7–52.0 mg·L−1, calcium 90.3–104.7 mg·L−1, magnesium 27.3–37.7 mg·L−1, organic matter 0.4–3.9 mg·L−1, chlorophyll a 0.7–132.3 mg·L−1, and bicarbonate 219.3–248.7 mg·L−1. The analyzed physico-chemical parameters were almost not exceeded the maximum permissible limit of WHO and Algerian Water Quality Guidelines. A total of 53 taxa belonging to 4 divisions have been identified, including Chlorophyta (52.83% of taxa), Bacillariophyta (28.30%), Cyanophyceae (16.98%), and Charophyta (1.89%).