Water Contaminations bring not only great damage to the ecological balance, but also serious losses to the national economy. The results of existing methods, which are used to calculate Economic Loss of water contaminations, are not able to reflect the problem explicitly. In view of deficiencies of those calculation methods, and on the base of mechanism model of pollution loss, the logistic equation and environment value theory, this paper first proposes to construct Logistic Model, which is invented by Belgian mathematician Verhulst in 1938, to measure Economic Loss of water contaminations applied to East Lake. The Logistic Model can not only suggest the relationship between pollutants concentration, discharge amount of pollutants, the value of environmental resource and economic loss; but also can quantitatively weigh the loss degree about environmental pollution for resources value. It can reflect the real truth objectively by using Logistic Model to perform “S”-type nonlinear behavior of Economic Loss. At the same time, the calculation method is simple, universal and easily to understand, especially when there are multiple water contaminations in water. The experimental results in this paper can describe the Economic Loss of water contaminations in East Lake accurately and comprehensively, in addition, it is able to help the relevant departments to establish measures to prevent and control water pollution.