The ratio or lake perimeter to lake area is proposed for the estimation of a trophic status of lakes as all integral parameter. A trophic status of lakes located on territory of the Shatsk National Park is being analyzed. Advantages of this parameter are confirmed by comparison with other parameters (Carlson index, chlorophyll index, oxygen concentration). The are the following.: simplicity of determination (from the mapping documents), stability to short-term changes or meteorological conditions, possibility of application at the development of strategy of lake treatment.