Models for analyzing water quality environment should be developed and used properly according to the objectives of analysis, the degree of water pollution, hydrological and hydraulic properties and topographic conditions of the research area, the target of water quality improvement (items, concentration, reference points, etc.), the measures for conserving water quality, the type and amount of data which can be acquired, required accuracy, time, money, the number of persons and computers which can be used. Therefore, a number of model types have been developed and classified by constancy of time, methods for dividing the space of a water body and handing of biological reactions. In this paper, the authors classified the models for water quality analysis. Then, the prerequisites and the processes for constructing the models were defined. Finally, examples of analysis were introduced. Objective areas included watersheds and water bodies, such as irrigation and drainage canals, rivers and lakes. It is important for analyzing the water quality to constrict a balanced model that simulates the process of pollutants flowing into a water body, hydraulic motion and reactions within the water body itself, because the accuracy of a system or a model as a whole is determined by the least accurate subsystem.