Ecological system depends on every link in the food chain. Last decades the majority of surface water is preserved into canals or collectors of waste water from urban environments. Phosphates and nitrates from artificial fertilizers, different detergents in large amounts reach the surface water and may change the ecological system, which cause the appearance of new types of algae and other aquatic plants. This phenomenon is an indicator of water pollution with phosphates. Object of study of our paper was to define the quantity of phosphates in the water of Lake Ohrid. For this purpose we have made determinations in three sample: Peshtan locality, in the beach of Ohrid and the location near the town of Struga - Kalishta. Phosphates were analyzed by the SF Method UV - VIS-type DR / 2000 Hatch - Lange.